SEx derives from the fact that the SE/30 is the love child/bastardization of the SE and IIcx. GttMFH2e says that the sire was the IIx, but the press of the day described it as a IIcx scrunched into the SE form factor.

With grayscale and a cache slot in addition to the PDS, it could have been so SExi indeed. B&W and just an '030 PDS made it kinda MEH for me back in the day. I had one for a while, a freeb from Goodwill in Da Bronyx, but I never even bothered to put the network card in there.