If someone is doing this contiously, then it could possibly become a bannable offense. AFKing isn't a immediately breaking the rules right away, as in real life circumstances could happen that force the player to leave the PC/console quickly.
It only becomes a problem if it happens a lot and it gets reported and the reporter states that the person is always afk if they match with them. That's when it becomes a issue and bannable. In your case, you seem to want to do it over the course of several games - then yes, it could end up in a temporary ban.