75mph ST tire

I have never seen any tire manufacturer advertise or recommend their LTs as suitable for TT use.

Of course they don't say that in their tire adds. As Michelin found some customers didn't like the idea of using a expensive tire like the XPS Rib on their suv/pickup.

At one time a few years ago their XPS Rib add said;

*Michelin® XPS Rib® tires are the best value per mile in the Michelin commercial tire lineup and an ideal choice for commercial trailers because of low rolling resistance (for better fuel economy), a long-wear tread design and retreadability. These tires also have the strength of a reinforced all-steel construction for lasting durability.
Responsive handling helps you negotiate through tough traffic
Greater durability and puncture resistance from a third steel belt.
Easily retreadable all-steel casing
Lowest cost per mile in this category
Resists sidewall damage with the sculptured sidewall protector.
Sidewall: black serrated
outline lettering.
Load Range: E
Service Description: 120/116Q *
Michelin 1-800 tech folks has said marketing recommended dropping this add in favor of the current one.

Think about it. Some folks have no idea on a the subject of tires and most likely would pass up the Ribs even though it was possibly the best tire for the money simply because Michelin says it was recommended for commercial trailer service.

IMO euro and Asian sizing with their "all position" tire designations makes good sense however some Americans have a mind set that a tire has to be either a ST or LT or P designation.