It’s the .
Seriously, though, yes. Might be a cookie thing as Hans suggested, might have to do with your messages to email going through Gmail, whatever the technical aspects, but generally, yes, evolving ̶r̶u̶d̶e̶ smartness.
I do use Gmail and “its ecosystem” for several reasons (and it’s great for what I need there) but it’s good to be aware of it and to keep things separate as much as possible, ideally use mail providers like protonmail, tutanota et al. for private things where using Gmail isn’t a big advantage (apart from being used to it/wanting just one email to deal with, etc.) and try to get family and friends on board of your preferred alternative too, cause if just you use such a service but the other party uses the nosy and keen to advertise ones, well… (However, if you want to use such an alternative for free, make sure to check their limits as you’ll reach the storage threshold much faster, and that means either paying or spending time on deleting the non-essential. Which isn’t the worst thing either, though.)
As an aside, that message wanting you to confirm an account someone created, could well be spam but there’s also a possibility of someone accidentally using your Gmail by typo.
Pretty much all Gmail address names that aren’t long random strings of characters and such are used up by now, the probability of someone owning almost the same address as you and maybe making a typo is getting ever higher, plus some sites for whatever strange reason still don’t require you to repeat your name (or password, for that matter when you sign up to mitigate typo errors ).
I got mails for someone else’s FB account on my gmail account because that person accidentally had used my Gmail address to sign up there, their actual name turned out to be the same as my gmail address save for 1 character. I had to solve that issue in an unorthodox way because customer support of especially some big companies these days can be very hard to get a hold of and even harder to get to do something useful (from all customer supports I had to contact in the last years, BTW, Fiverr’s was absolutely top both in response time as well as in actually doing something about my issues).
Or it could be some other kind of mess, if you Google a bit, you can find enough posts by people who receive “legit” mail that’s for someone else on their gmail account.
Or you could ask discobot maybe they know more …