@blackyps
It makes sense to have the option to do 3v3's in TMM. People can queue for multiple things simultaneously.
Numerous players do like to play 3v3's. Also, sometimes groups of 3 friends want to queue together for 3v3's where they are the entire team (without a random 4th teammate with them).
If you need help finding good 3v3 maps, I can help with that if you'd like, and there is also the option of having the 3v3 queue mostly or entirely use map gen maps, if desired.
PS: Having multiple 4v4 TMM options does not have to be mutually exclusive with having 3v3 TMM available.