Question about implementation of matchmaking

I'm wondering if the matchmaking algorithm is either of the three following ways:

0) does it first let you find an opponent and then randomly choose a map from the not banned maps of both teams.

1) or does ist first randomly choose a map and then pairs you with an opponent with the same choosen map?

2) something else

(1) would lead to a uniform probability of getting one of the not banned maps, but has the disadvantage that you need to que longer and maybe explains the fact that you aren't allowed to ban more then one in Team games.

(0) gives a a non uniform distribution for the not banned maps, wich is anti proportional to the average amount of bans for each map. But this means not liked maps are less likely to appear. Additionally it would allow to ban more then 1 in Team games. And reduce the waiting time in comparison to (1).

I would personally think (0) is the better version. But I don't know if it's (2) 11.

Also im wondering if it's not (1) for what reason the ban restriction in TGs exist?