I "deleted" my account three years ago, and just before doing so I changed my name to something nonsensical, and I created an alias email address on Outlook.com

I "deleted" my account three years ago, and just before doing so I changed my name to something nonsensical, and I created an alias email address on Outlook.com, set that as my primary email account on Facebook instead of my real Gmail email address, and then applied for a permanent deletion. I still have the confirmation of the"permanent deletion" from Facebook in that fake outlook.com account. Back in November I started getting Facebook spam on my Gmail account, the "people you might know" your emails, and there were people I knew. I clicked on an unsubscribe link that led me to a login. Out of interest I used my Gmail account and reset my password, and within thirty seconds I was back in my account. It was exactly the same account as I had permanently deleted. My assumption is that someone screwed up at Facebook and ran a query that updated permanently deleted accounts. I'm not sure what else could have caused this to start so spontaneously after years of peace.