I think there's some confusion because Multimorphic made sort of an unfortunate naming decision with the P3 Pinball Platform and the P3-ROC, which are two completely different and unrelated things.
There's classic P-ROC, drop in controller replacement for Stern/WPC, with switch matrix, DMD, Aux bus support, etc.
There's the P3-ROC, which is a similar to the P3-ROC like Ep said except it's for new machines, so no DMD support, it uses all direct switches, has an accelerometer on board, etc.
Then there's the P3 Platform, which is the new "entire playfield is a video screen" thing.