I personally am very skeptical of the alleged real uniqueness of trailer rated tires, other than its a legal escape clause for manufacturer liability. Weight limits and size are of course another matter. Semi's often have all position tires used, steering, drive and trailer.
I don’t know why you’d doubt an ST tire is a specific build. Sidewall flex is the issue and thise are stiffer. You don’t run them on a truck because they’d beat you to death.
Running an LT tire on a trailer reduces the load rating by 11%. Due to sidewall flex they run hotter and hence the derating. I dunno if you’d get a ticket for it or not, but I’ve seen them on trailers for years and years.
