Goolge can't even get their subsidiary use their own 2FA tools
While I expect that this has more to do with ensuring they have your cell phone number, it is a shame that Nest didn't deploy Google Authenticator instead of SMS. Text messages fall far behind most of the other 2FA solutions. They fully depend on multiple third parties, any one of which can remove or inadvertently break security, or pass what should be a secure message with no security at all.
On the flip side it also costs more and requires always on phone/network connectivity.