By your definition, Lenovo ThinkPads, Dell Inspiron, etc, aren't PCs, they are they own line of computers.
Laptop and desktop form factor, check. x86 based, check. Unlocked bootloader, check. Run general purpose OSs like Windows and Linux, check. Mac are PCs too.
I think the x86 architecture is not even needed, it is the form factor and be able to run non Apple OSs that make them PCs too.