I spent 15 years in the passenger and commercial tire business in my younger days, it was the family biz. I don't recall seeing much from the trailer crowd as far as issues and everyone ran LT tires then on trailers. ST tires didn't become the norm until around '98 or so. Somebody thought trailers needed a special tire, I've never seen so many tire failures as I have with ST tires. I've run LT tires on every trailer I've had without issues and have no problems using them at all.
When we bought our current trailer new in 2020 it had Goodyear Endurance ST205/75R15 D 107N load 2149lbs @ 65psi max on no name 15x5 alloy wheels rated @ 2200lbs. I gave them a chance, what a mistake that was. First trip 300 miles into it a blowout, 4 months later another. Done. Replaced them all with Falken AT3/W LT235/75R15 E 116 load 2756lbs @ 80psi max on Sendel alloy trailer wheels 15x6 @ 3400lbs. Not only do I have a much safer rating for the 7,500lb trailer, it rides so much better, tracks better, has twice the tread depth vs the Endurance and so far with 15K virtually no wear at all. And I've seen none of the scrubbing wear I did on the endurance.
As for the sidewalls not being up to the task at hand, I'll call BS. These Falkens are AT and made for abuse at full load or aired down they'll take far more abuse than any ST tire, and in those conditions the sidewalls flex way more without failure.