They are inexpensive enough that if you screw up, it won't matter much.

We don't believe it's too trendy at all. A butcher block island can add a beautiful focal point to your kitchen. A client of ours just had a walnut top installed a few weeks ago. Best of luck!

Butcher block is not a good surface if you have a sink mounted on it, or if there will be the possibility of frequent water spills. In addition, many folks do not want butcher block if there will be food prep or eating on it, due to the difficulty in keeping clean and safe.

It is a transitional Farmhouse [...] are butcher block islands timeless or too
trendy?

Considering aesthetics only, a butcher block island/counter/table is right at home in a farmhouse, depending on how it's executed, IMO. If you have a relatively narrow island, in a simple rectangular shape, and *especially* if it's freestanding (or has "legs" that give it a freestanding appearance), then it won't be trendy because it fits the style of the house.

And, like Mr. Joseph pointed out, you can resand, oil/stain, or replace, fairly easily. I, personally, would not use it as a food prep surface (but I always use cutting boards or platters, even on stone or solid surface counters), and I'd forget about using butcher block at all if there was a sink on it, or if there was a cooktop on it.

I have a small, mobile, butcher block island in my kitchen (not in the center, and not for food prep), and I like to use it as a pantry landing space, table linens and garden seeds storage, and snacks (fruit bowl).

Wood counters, including butcher block, are timeless in my opinion... but you can make them more trendy. This is our remodeled kitchen, my hubby designed and built all of the cabinetry and the waterfall wood island. We used walnut and preferred long boards as opposed to a proper end grain butcher block. I believe the waterfall edge makes the wood counter more trendy than typical, but it's a look we love so we were ok with that, and I am proud of my hubby's craftsmanship because I know firsthand what all went into building that counter.
You'll notice that we DO have an under mount sink in our wood counter. We have ZERO issues with water because I used Waterlox to coat the wood (extra coats around and under the sink) But I also do not use my wood counters without cutting boards. (Waterlox IS food safe, provided you don't have an allergy to tree nuts, but it DOES show cut marks, so I never cut directly on it.) I would never use Waterlox on an end grain butcher block that I intended to use without cutting boards... and I personally wouldn't put a prep sink in a proper butcher block either though I know people have done it successfully for many generations.
I do think a wood counter is a higher maintenance surface, but I think it's mostly timeless as well. I think it fits into most any style of home because so many different things can be done with surrounding cabinetry and different edges and finishes. I think it's not used as often because people are scared of it, it's not actually all that inexpensive, and most people want the least amount of maintenance.