Giving benefit of the doubt maybe they still do the speed rankings of the past while at the event. When I used to go, you named your speed and the person closest without going over in I think 5 mph increments won that speed “class”. The results on the site only show classes by drivetrain and Fi/nonFI. 

The Texas mile works kind of like the final showdown on price is right. You guess what your top speed should be. That is your class say 160-164. In order to win your class you have to be fastest run in the bracket without going over.