You're right only 87.8 percent of personal computers have Windows installed as the operating system. Then you have MAC's with 9.6 percent, although I'd almost say since most people explicitly call a MAC a MAC and that a PC usually means not a MAC in most peoples minds. And then the whopping 2.6 percent that use Linux, ChromeOS or god knows what.

So ya you can stop being pedantic because when people say PC they almost inevitably mean a computer running windows so yes although not technically correct when that's what the word means to most people that's what it means, that's kind of the entire reason why language develops overtime like when we invent new words or change entirely what a word means.