You claim OpSec, but if you’re using such bad opsec, then I’d suggest you’re not actually doing opsec. Tying a throw away account to actual data that can directly identify you is just such bad opsec, you might as well use your actual name as your user name.

Opsec can be a relative term. Yes, some people are selling drugs or spying for the Russian government but other people just don't want to be OSINTed by scripts like this. Then creating a new Gmail account from the same IP address is enough. It's a lot easier to hide your identity from people who don't have the power to issue subpoenas.

IP address != phone number

I think his point was that he wasn't looking to be totally invisible. Just less obvious to people who won't spend a pile of time looking for you.

If you're adding your phone number to a throw away account you use on Target or Walmart, it's likely okay.

The IP comment was likely because if someone can get your phone number from the Walmart service (via subpoena), to track you down, they can also get your IP address too.