DOT Endurance Test for ST Tires NOT same for LT Tires

I have no doubt LT will hold up better than an ST at respective max load. At the same time I also believe an 87 mph rated ST is better than a 65 mph ST. Even if DOT runs the test at 55 mph. I don't think the DOT test is intended to be a failure test as much as a test to measure heat etc. to predict it meets the minimum standard to be on the road.