As I have understood it, was taught at the university level, and have researched extensively for papers at college, the "press roll" (although considered a generalized term now) originally referred to the technique of pressing into the drum while rolling to get a louder dynamic out of the snare drum, but is done without the "release" half of the rolling technique.. It is used for performing a buzz/closed/orchestral roll at loud volumes.
When you do a ppp roll for a symphony piece in a concert hall, I don't consider that a press roll, since there is no actual "pressing" going on.
I'm a stickler for preserving accurate percussion terminology, sorry. I mean, just check out my posts in any of the "double stroke roll" threads.