Ironically when I tried to set up a legitimate Gmail account for my business and used it to set up several accounts, within few days it got locked with no recourse for unlocking - there was a comment box where I could beg for an unlocking, never even got a response though. So Gmail is only for throwaway accounts from now on.
Maybe it's location specific then or something...
All you get asked today (at least in Australia on a residential ISP) is a first name, last name, password, date of birth and gender (includes "prefer not to say").
Years ago I think you were correct, a phone number and SMS verification check was mandated, and each phone number could only be used so many times on different accounts.
[1] https://www.androidauthority.com/gmail-without-phone-number-...
It's about as awful as discord, who also locks account creation behind providing a phone number when an account is created from my residential IP. It almost feels like I've tripped some prevention mechanisms that all these companies are sharing and I have no idea of how to get my "goodness" score back up.
You should not have too, though. And as the discussion shows, Google requiring a phone number depends on luck.
As I've noted previously (<https://news.ycombinator.com/item?id=30953159>), I recall but cannot find the 2-ZIP-code example, though a paper describing four location points IDing 95% of the population uniquely is here: <https://www.nature.com/articles/srep01376>
ZIP + gender + date of birth is another highly-effective identifier, with 87% accuracy:
"What Information is "Personally Identifiable"?", by Seth Schoen: <https://www.eff.org/deeplinks/2009/09/what-information-perso...>
Latanya Sweeney, Computational Disclosure Control: A Primer on Data Privacy Protection (Thesis, 1977, Massachusetts Institute of Technology)
<https://groups.csail.mit.edu/mac/classes/6.805/articles/priv...>
"ZIP ruled personally identifying in California" (2011) <https://www.identityblog.com/?p=1168>