That's interesting... My buddies
L5240 has Cat2 lower ball-ends, but it's practically identical to my MF1652 in specs, and mine doesn't accept Cat2. But, I like your topic. I think the blurred lines are getting even more blurred. We now have several brands that offer 60'ish HP and Cat1/2 hook-ups, which can be had with HST or Gear Trans. These include modern loaders that can lift 2500+ lbs.
Weight might be a good indicator, but there are inconsistencies with that as well. The 50hp Mahindra 5035 weighs quite a bit more than competing CUT's, but I wouldn't consider that a UT either.
Maybe we can use Transmission options as a factor? It seems that currently, what sets the CUT & UT class differential is Trans options. Anything HST is CUT and below. Anything without an HST option is UT and up ??????