To me, the slot is a place, and a bumper is a role/action.
Since we've got the pinball reference, there are plenty of places one can have bumpers on a pinball table, and there are different types.
I'm fine with either term here.
My first exposure to the term bumper in hockey is much older, referring to the Broad Street Bullies as bumpers and thumpers. Not power play related, obviously.