Tilt, I believe the "want" for the Yak-9UT has to do with the fact that its would be one of the simplest varients, in AH. In other words take the least time to produce and implement into the game.
Many people like the Yak-9U but due to its anemic armament, its not a truely viable aircraft in the MA. Small clip and no effective snapshot.
True there were only around 300 -UT's, but I can point to several other aircraft/armament options that are common in AH that have similar production levels.
I haven't looked the numbers up lately, but I thought there were more Yak-9U's than there were Yak-3's ?
Regardless, its just an aircraft that I know I would like to fly in AH
Plus it would be very easy to do