And what stops people from doing that with the current 6-ban system?
It was already pretty common for streamers to hide the client, during champion select, or at least mask mask the parts that would give away that somebody ghosting is in the same champ select (hide the picks/bans, maybe even the timers).
Actually, from that perspective, the new method makes it harder for people to tell if a streamer is on the other team, cause you won't see the other team's bans until the ban phase is done. It would be too late to do anything about it then.