It’s never too late to change important terminology and confuse customers, that’s what Oracle must’ve been thinking…
Security Patch Update (SPU) terminology is introduced in the October 2012 Critical Patch Update as the term for the quarterly security patch. SPU patches are the same as previous CPU patches, just a new name. For the database, SPUs can not be applied once PSUs have been applied until the database is upgraded to a new base version.
via CPU, PSU, SPU – Oracle Critical Patch Update Terminology Update.