Mmh no? I've been without FB account for 3-4 years, and recently opened a new one from scratch because some friends only use FB and absolutely nothing besides confirming my email was required.
Yes, it does suggest that I add my phone, and that I verify my friends, and that blablabla, but nothing else is required for me to add few friends and join a chat.
I'd been without a Facebook account for four years as well, but created one for testing/verifying the behavior of an application we'd recently gotten approved.
As far as I'm aware it would not let me create an account without a mobile number to confirm the account.
After performing a single action (creating a page), my account was flagged, and thrown into the facial recognition captcha process.
See here for many more anecdotes about this process:
My bet is that they were able to internally link your previous account and the new one. And probably kept building your profile while you were "without" an account.
Yes, it does suggest that I add my phone, and that I verify my friends, and that blablabla, but nothing else is required for me to add few friends and join a chat.