

Microsoft and LinkedIn blatantly ignore the GDPR in various ways, so while you’re technically correct, you may need to win several court battles to get that fixed. On the upside, it may bring in some extra cash when Microsoft refuses to update your profile despite of a judge’s order, but on the downside this process can take years.
In one recent case, Microsoft and LinkedIn decided that placing a tracking cookie before hitting “accept” on a cookie prompt was worth three years of court battles and €60000 + lawyer fees to ignore the judge’s orders. And that’s a case they lost, they’ve won cases as well. I imagine “we couldn’t verify ownership of the account through the email address” will make it quite far in court unless you send over a lot of personal documentation to prove your ownership of the account.
For EU citizens, they have to legally abide by deletion and correction requests. However, if you can’t prove you own the account (through your email address for instance), they can demand you show proof that you say who you are. If your name/DoB/picture doesn’t match, they can even decide you’re someone trying to do a malicious account takeover and ignore your requests. Fake data requests are easy to send and hard to catch without some strong proof of identification. Even knowing the account password may mean nothing if that password has been leaked before at some point.