This could be just a way to track pirated copies. First achievement comes from Steam statistics where the second one is from the game itself. This way you can track how many copies of the game are being pirated.
Not Steam, but interestingly some Microsoft published games will unlock Xbox achievements when pirated, presumably because they built the version sold on Steam to unlock achievements on both platforms. Pirated Psychonauts 2 and got the little under half you get on a casual non achievement hunting playthrough on my Xbox account
With the aggressively anti-user and poorly thought out moves tech companies have been making lately, I wouldn't put it past Microsoft to start using little discrepancies like that to go after people
It would be dumb, way more effort than it's worth, and likely extremely invasiv... Probably not likely, but I would've said the same about a lot that's happened in the last couple years.
But all the same, in your shoes I'd look into blocking that on the off chance it puts a target on your back
Was years ago when the game first came out, plus am a Gamepass subscriber now anyway so "officially" have a license (yadda yadda, subject to subscription running out or them deciding to drop a game they own from their catalog). But there's always a chance I suppose
As long as you're not doing it now I wouldn't worry, you'd need very detailed information to tell you apart from steam. Privileged information I'd never have considered Microsoft yanking a year ago, but a year from now? Unlikely, but not unbelievable anymore
Shooting yourself in the foot trying to punish users seems to be the new SOP for tech giants these days...I no longer would put anything past them