surrenders before 20?

recently i won a ranked game do to my enemy team surrendering. the odd thing about this game is that the enemy team surrendered before 20 min. is that a thing now? or has there been a bug. i am just curious. did i miss a memo?

to be specific the enemy team surrendered at 16 min no afks no disconnects. and yes the game was one sided and they all voted 5 to 0 to surrender but at min 16? not at 20... that is what has me so confused.