> This is a nice benefit of Google Fi. Since swap attacks are not possible with it, as customers support agents aren't able to do sim swaps.

Are you sure that this is the case? According to https://support.google.com/fi/thread/761170 there was at least one case where support agents moved a Fi number from a locked account to a newly reopened account, without the user being able to access the locked account:

> I call Google Support and the amazing Google Support rep I spoke to (The only good one I’ve talked to so far during this whole process) stayed with me for over an hour and worked with tier 2 support in getting my Project Fi number transferred to Account 2.

A SIM swap with Fi might be harder to accomplish than with a regular provider, but it looks like there's still the risk that someone manages to convince a support agent to move the number to a different account.