about 3 years ago - M.ArdA_TW - Direct link
Hello Spiff,
the reason behind it mainly is the lack of players for matchmaking. It starts as 6v6 but when it does not fill the game it starts the lower the numbers to 3v3 and it takes some time to fill in. It should be able to let you join a game of warmup phase when the minimum number of players is found by the matchmaker.