Your vocabulary is different to common usage. Since, well, the dawn of time, PC has meant "computer running DOS or Windows" to most people. We know there's a difference technically, but that doesn't change the common usage.
Doesn't stop me from giving grief to companies that casually mis-use the *correct* definition of "PC", and complain that they are saying "PC" yet have no Linux support. May not get them to port to Linux, but entertaining nevertheless.