Back in my day, we didn’t call them ‘personal computers,’ we just called them ‘computers.’ And they were all different. Atari, Commodore, Apple, Tandy, Texas Instruments, etc. If they were called anything they were called ‘micro-computers’ because they were smaller than a warehouse.
It wasn’t until IBM (late in the game) came out with PC that computers were referred to as “PC’s.” It was still before the first Macintosh came out, too.
When the clones came out people just referred to them as PC’s instead of PC-Clones. When all the other computers went bye-bye it didn’t leave anything else besides the Macintosh and IBM PC and its clones.
So, if you want to be pedantic, an Apple computer is not a PC because it’s not a clone of the IBM PC. It is, however, a personal computer.