20 seconds is too short ...
Cause sometimes i wait to click ready, cause i'm fed up with players who makes game with 8 players, and when u join they click start and u play a 1vs1 that u didn't want ...
So sometimes now, i wait for more players joining before click ready, cause for me when u join a 8 or 6 players and u play a 1vs1, i feel like just trapped

PS: and i know some players do that for the rating, cause they have 50% to be red, and some chance that their opponent surrender ...