You don’t have to do anything. It depends on why you are doing something. So, why are you benching in the first place; what is your goal?
90 degrees isn’t a bench press, it’s a partial bench press - similar to a floor press, or board presses - and can be utilized for a range of reasons including overloading the movement in raw lifters (as in, lifters with no specialized lifting clothing), training a weak area, or for bodybuilding purposes to target a specific area. Shoulder injuries can also be a reason to use a limited range of motion. Etc, etc.
What I’m getting across, is that is you are going to shift away from tried and true methods of doing something in lifting, you should know why you are doing it, and the potential benefits & drawbacks.
It honestly sounds like he’s full of it though, doesn’t know how to properly bench, where elbows are tucked on the way down, then flared about halfway up the lift.