There are few problems with this 6p start (low player count). Major is that it makes server custom but I heard it's planned feature?!?
But then other problems:
When you enable low player count on, it shows correctly 3/3 required to start the round. But it's working only like that 1st round.
When you break preround with 3/3, then it shows players needed 15/15 -but it really needs stilll 3/3 but this makes some people to leave.
Then after server has gone empty, it will show player needed 15/15 again, even it still required 3/3.
Only way to "fix" this on empty server is to turn off low player count, update server, turn on play lower count again and join server.
THen it shows again 3/3.

(also we need possibility to turn idlekick off but it's another story).