He means to say 'death of PC gaming on a Mac' because some people forget that all computers that are stand-alone for a person to use are "Personal Computers" (and not mainframes which is what the distinction is for).
If you call a Mac a PC, you'll only confuse your interlocutor. No-one ever refers to Macs as "PC", except to point out that "Macs are 'Personal Computers'".