Rincon ( or anybody else wanting to read the trailer manufacturers position on this ) I would suggest you check out the owners manuals for some trailers. Many are available online.
I can tell you the owner manual for my Titan horse trailer and my Load Max ( Load Trail ) equipment trailer both state in the manual that fitting either LT or ST is appropriate to their trailers. Same with 4Star horse trailers, and the above mentioned Platinum.
The new Platinum I am buying will have LT from the factory.
In the case of horse trailers, it's typical what I see is only the higher priced trailers come with LT.
Airstream travel trailers fit Michelin LT tires from the factory, either standard on some models, or optional on most other models.