The roots got chopped because of this heaviness of the soil, even as small as it was the ball was still heavy.

Also there is the problem of all the soil that is removed from the field every time a crop is dug - the smaller the balls, the less soil that is lost. And...

Most B&B trees are grown in a soil with clay characteristics so that when the tree is dug the
root ball it will hold its shape: sandy soil will simply fall away from the roots. The clay soil not only
maintains its shape but also retains water, so that B&B materials are usually more stable in terms of
optimal water conditions during the time they are out of the ground. When the tree is planted into the
landscape, however, the clay character of the soil is often different than that of the surrounding native
soil. Differences between soil textures will impede water movement and therefore inhibit root
establishment.

https://s3.wp.wsu.edu/uploads/sites/403/2015/03/bb-root-balls.pdf

I planted a balled in burlap Kousa dogwood once, without disturbing the field soil ball. I couldn't keep it hydrated during the summer and the top just dwindled away. When I dug the tree out after at least two years of waiting for it to establish and progress there was very little root growth extending beyond the field soil ball.

Which was dust dry on the inside, despite winter rains and summer watering during the whole time it sat there.

I have had the same experience with at least one balled in burlap magnolia.

Probably most ultimately balled in burlap stock is grown in small pots - with the same problem with growers leaving the plants in them too long, as with plants intended to be sold growing in containers - before being lined out in fields.

Nearly all of the feeder roots are cut off when balled in burlap stock is dig and covered with burlap anyway.

As usual, your experience is much different to mine. Liners are often directly field planted. And most B&B stock is root pruned prior to digging for harvest...often as much as 6 months in advance. And this is done specifically to cause regeneration of feeder roots within the pruned root mass.

Well, it's already planted, so what will be will be. I had to hack at it because there were no roots in a large portion of the ball -- just tightly packed clay. Of course, when I finally got down to where I saw roots, I wasn't as heavy-handed, but still -- it wasn't that easy to free those roots. I absolutely believe I did the right thing -- like I said, my native soil is very different in texture; I'm confident the tree will be fine. :0)

"Proponents against maintain removal pulls off too many of the fine
feeder roots in what is already a highly compromised root system and
therefore makes the tree harder to establish and with a longer period
necessary to do so than if it were left intact."

Very true. You can see this when buying bare root. The large Oregon nurseries that grow in heavier soil have bare root stock with noticeably less fibrous roots than those who don't. I'm not understanding the reasoning behind completely removing the clay. I definitely know the problems when planting a light soil tree ball in a heavy clay hole. But why the problem the other way around? Why would a tree not easily and readily push roots into the surrounding lighter soil?

Also, if the people digging the trees are properly trained they would know to always check for the root flare and shave off any excess dirt if need be before finishing the balling process.

"Probably most ultimately balled in burlap stock is grown in small pots -
with the same problem with growers leaving the plants in them too long,
as with plants intended to be sold growing in containers - before being
lined out in fields."

Really? The larger nurseries that I know of here in the Twin Cities area are all lining out mostly bare root. The only exception tends to be with oaks, which are being lined out with root bags/grow bags/small dirt balls, etc. Oh, and potted birch clumps maybe.

My experience echoes GG's...with trees being undercut, sometimes a whole season, but always at least 6 months before digging. Hessian (burlap) seems to be going out of favour (but less so with evergreens such as yew). I have noticed a changeover from nurseries still growing young, field-grown stock to be sold on as maidens, to the long term use of perforated pots on a permanent irrigation line, sometimes for years...because many people are prepared to pay £££ for BIG trees (the fools). In short, there appears to be no overwhelming 'correct' way to do this since the trade is catering to such a diverse set of needs.

"Also, if the people digging the trees are properly trained they would know to always check for the root flare and shave off any excess dirt if need be before finishing the balling process."

The flare was completely covered by soil.

I plant a lot of B&B material and the condition of the plants vary. I only plant woody plants in dormancy, which gives me more latitude in how I treat the roots. I try to get rid of as much of the clay as possible, but I try to do it as gently as possible. FWIW I have never seen any B&B stock with circling or congested roots; the issue that i have encountered is root balls that are too small. .However I have had good luck with B&B stock, even quite large trees (Cercidiphyllum, various Acer, Thuja come to mind).

Almost all B&B stock is buried too deep, but most container stock is, as well.

Root pruning being beneficial depends on the replacement roots not being cut off when the plant is dug up later.

"The flare was completely covered by soil."

Covered by how much? How deep?

River birch love clay soil, by the way. The fastest growing trees I have not named "willow" or "poplar." I've had 2' clump liners turn into 10'+ clumps in only 2 years. They root into the clay like mad.

Does anyone cut the burlap during planting?

Removal of any burlap around the trunk and off the top half of the rootball is always recommended.

They are making burlap thinner and thinner these days and it can rot and disintegrate surprisingly quickly. I know wholesale yards where, if a tree remains after a second summer, the B&B tree ball has to either be re-burlapped or wrapped in plastic to be able to ship.

I have always removed the burlap. In the same vein, I never plant in those fiber/coco pots plants are sometimes sold in. I don't want anything in the way of those roots finding their way into surrounding soil - the faster the better.