While I cannot comment on tire compounds and construction, I can say that the primary reason the RV and Tire industries recommended ST tires is their stiffer side walls and the rolling resistance of their tread design. These characteristics and a recommended speed rating of 65 mph are what the industries feel is proper.
If a person feels they are wrong or these features are less important than those found in LT tires, so be it.
There are not enough LT tire in trailer use to draw any meaningful conclusions of performance, when compared to the millions of ST tires placed into trailer service every year.