If anyone's curious the AEK with SKCM Orange that has the longer/deeper stabilizer is a 138,XXX serial no, while the AEK with SKCM Salmon and the same size shorter/shallower stabilizer as the AEKII was a 8XX,XXX serial no.
EDIT:
Also, they changed the location of the inserts for the plate, which is likely another reason it's deeper. The old AEKs have the inserts on the top side of the keycap, while the newer AEKs and AEKII bottom side. So if you're giving this to someone to use on a new plate, they're going to probably have to get new inserts and wire.