@AdaraAstin i looked a bit more and found this. it's a bit wordy about RCS but also addresses the risks of phone verification and multiple accounts
(kinda very shit that we have to read this from kaspersky instead of google since it's technically an unofficial source, but welp. google itself doesn't want us to think about this clearly)
https://www.kaspersky.com/blog/google-phone-verification-rcs-2026/56162/