accepting invite while in queue doesn't end well

queued up, was declaring my champ, got an invite from a friend, accidentally hit "accept" instead of "decline". all other players 'left the room', my countdown finished, had to wait for a few seconds, ended up on the home screen, and now i'm getting a "joined queue failed" error telling me i abandoned a game.

the temporary ban i understand, i clearly abandoned a match, but why was i able to accept another invite while in queue in the first place, though?

not sure if it's a bug or if i'm just an idiot, i'll let you decide that.