PC has been coopted by Microsoft and gamers to mean an x86-64 box, and it kind of applied to Intel Macs since they could run Windows and could have graphics cards (specifically the Mac Pro which had PCI-E slots and was really just a traditional PC that happened to be macOS certified and shipped with that OS.
So yes, it's a specific kind of PC. It's like saying a truck is a car. Yes, technically, if you wanna split that hair, but it's not like people calling it a truck are wrong. And maybe they are proud of what they have, but they're also just trying to be accurate and not disingenuous.
By saying it's a Mac, I avoid people suggesting I run tools only available on Windows. However, I attract haters. I'd rather be concise and informative than well liked. I don't care that you or the next guy doesn't like Macs, but yes, I'm going to call it what it is, because while it's also a PC, it's different enough and I'd like to avoid the chain of conversation that comes with "just use X app" and then I have to say "it doesn't run on my platform" and then we're back to here with the haters. So I just cut out a step.
Yeah, it's not so much gamerscore as it's gamer history. So if you look at my gamerscore, the actual number of points doesn't really matter, but you can see I've been gaming on Xbox for like 20 years, I've played so many games, you can judge me as a gamer based on what I've played and how far I got. It's not fair to mistreat a person based on gaming preferences, I'm just saying you get a clearer picture. So on mine you'd see a lot of RPGs, action/adventure games, point and click adventures (Dontnod/Telltale stuff), and Metroidvanias. You wouldn't see many sports games, racing games, or simulation games, and that would tell you things about me as a gamer.
Of course, I'd been playing video games for about 20-25 years before I ever heard the name "Xbox," but that's not tracked.
We could get into how achievements are just a stupid collectible for gamers, but are used by Microsoft to monetize anonymized gaming metrics to inform publishers how their games are played. Not all of them care, and this service is part of what Microsoft charges ~30% for, it's not an extra service. Some do, and most famously to my knowledge, it's why you didn't get an evil path in Fallout 4, because an overwhelming majority of Fallout 3 players went for the good karma achievements. Fallout 3 gave you achievements at levels 8, 16, 24, and 30 (the cap), but it also noted your karma level (good, neutral, or evil). And at each level it was like a stupidly overwhelming win for good, so they assumed most players didn't want the evil option. I mean, they did give you a couple evil factions to work with (the Institute if you were scientifically evil, and the Brotherhood of Steel if you were militarily evil), but ultimately your character is a good person.