I've been using two separate accounts, also always via VPN. My account was immediately blocked until I provided a phone number (doable but a chore to have a private number).

Same with the other account.

An attempt to remove an "optional" and totally not mandatory phone number results in immediate account block "for my own security" and a request for the number.

You might be an outlier.

There are servers that require a phone number to have been provided, I think in an attempt to stop harassment and sock puppets.