That you have not reached this limit indicates that you are doing a good job! 
Tell the interviewer that if the limit is reached, then there is a design error.
If the interviewer presses harder, then there are two technical solutions. The first is in the authorizations tab of PFCG to use the "read old and merge new" option via the "Expert options". This you are probably doing hence you don't have the problem, but it can also be triggered manually within the menus in the authorization data.
There is one more joker you can play, but you must first tell the interviewer that they are using "Edit old data" to support a design error in the way they build and maintain roles.
Cheers,
Julius