My guess is they fixed whatever weakness in their rate limiting allowed an attacker to automate requesting millions of password reset emails. The fix could be as simple as adding a new CAPTCHA to the password reset flow.

Yep I got 2 on Jan 9th. he e-mails come from security@mail.instagram.com

I also get a bunch of these e-mails from them every few weeks:

Sorry to hear you’re having trouble logging into Instagram. We got a message that you forgot your password. If this was you, you can get right back into your account or reset your password now.

So, I guess you can actually message them, pretend to another user to rese password? I don't follow many people or have many followers. I can't imagine the attempts on other higher valued accounts...

I get those for account I never registered or confirmed email for. I just keep reporting them as phishing they are...

I’m 100% convinced they send those out purposefully to encourage users to log back in.

Same, it's very weird. Only ever IG.

Got one a day or two ago again actually.

Same here, I got one on January 9th.

I honestly thought it was a "hey, we're still here, you should log in" dark pattern. (My account's been unused for years).

I mean, if they knew who was requesting the password reset, then you wouldn’t need to reset the password, just accept whatever auth mechanism allows them to know who is resetting the password.