Without knowing anything in particular about seaplane ops, it could be to give the rather underpowered aircraft of the time (Late twenties-early thirties) a better chance of getting airborne in a seaway if that makes sense.
With such high catapults, the space between them (and forward of the hangar) would remain clear during catapult use. Perhaps this was valued as a working space (unfolding aircraft, etc).
That was kinda my thinking, a space for running aircraft in and out of the hanger, unfolding wings, etc.