Earlier quoted context omitted.
To be fair, they did say "PC" specifically. It's not uncommon to consider that a category that doesn't include Apple (e.g. the "I'm a Mac" "I'm a PC" ads from years ago)
People just need to quit using the term "PC" to refer to desktop or laptop hardware that happens to be running Windows. Laptops running MacOS are "personal computers," as are desktops running Linux, or effing phones running Android, for that matter.
I think the issue is that there's clearly as need for a term for the category of "things that usually run Windows (but you can also probably put Linux on it, and like, even one of the BSDs if you're feeling adventurous)". PC isn't a great one from a linguistic perspective, but there's not an alternative I've heard that seems likely to catch on. There probably also should be a better term for "laptop/desktop", since as you mention "computer" itself is not really narrow enough if you're being pedantic, but at the end of the day, right now the only really differentiator we have is context. In the context here, it was honestly more clear clear what was meant by "PC" in the top-level comment than it was whether the person responding to it actually misunderstood or was trying to make a point.