Here is a picture of around 14-18 inches deep stratified vs. around 24 inches deep stratified. I didn't expect the difference to be so stark.

Imo I prefer to do the mixing as I add organic materials. I believe you get a better synergy that way. What you have there is a loose layer on top that likely is kind of low in minerals and colloidal gels, and a heavy clayey layer below that.

It does not appear to me that there is any organic matter in those soil tests.
The one in the "Mason" jar looks like sand while the one in the other looks like clay.

To my eyes there is a lot of compost looking organic matter in the upper layer of that hole. It may be that the worms are not going down into that heavy clay as fast as you would like. However, do you really need soil 20+" down to be heavily amended? How deep are the roots on what you are trying to grow?

One other thing to keep in mind is that if you were to double dig into that underclay and amend it so it's much more porous, in wet weather it may act like a bathtub and the porosity would fill with water.

Just some things to consider.

The root zone, rhizosphere, for most plants is about 6 inches down, so spending time and energy trying to amend soil 20 inches deep is largely a waste. Over time the Soil Food Web will amend that soil as is necessary.

Roots may go deeper than you think.

Here is a link that might be useful: Root Development of Vegetable

I agree that roots can go deeply.....IF the soil is loamy like the Nebraska link.

I've had great results from planting tillage radishes and covering frost bitten radish with unfinished compost. My worms don't care much for finished compost.

Looking at the color of the soil, and looking at your zone number, 8a, I'll assume you live in a place that's hot most of the year. From what I read, it looks like you have oxisol soil. I don't think you have any easy recourse. Raised beds are the right answer. The addition of organic material will take a very long to time to transform that soil.