When the mechanism first appeared, banning ninjas meant banning ninjas from the opponent's ninja pool, so as long as you see the interface, all the ninjas belong to the opponent.
In ANBU rank, you can choose to ban 2. At this time, if the opponent only has 2 powerful ninjas who are banned, the rank match will be difficult to play, and it will not be very friendly to novice players. At Shadow level and above, you can ban 3 ninjas, basically those ninjas that no one wants to see.
The current ninja ban mechanism bans ninjas from all ninja pools. The advantage of this is to prevent novices who only have one powerful ninja from being unable to win the rank match. At the ANBU level, 2 ninjas are banned. For example, if a Jonin 3 matches an ANBU 1, he can ban 2 ninjas from the opponent. There are 3 for film level and above. This is the same as before, but both sides don't know which ninjas the other side has and often can't stop what the other side is best at.