This is absolutely still needed. Good suggestions above re: 1) quick and easy fix = "Confirm" Button, and 2) a true join and re-join, doesn't see like it would really affect the matchmaking workload much, and/or 3) why not do all the matchmaking once everyone has joined?
I am often whipping in and out of different modes in the game and this is very easy to do. And, this one quick click can ruin 4 weeks of a GAC season (by wrecking one whole cycle and thus severely hindering your chances to hit a top score/Kyber). Pretty unacceptable, CG - please just add the confirm button ASAP.
