I think almost all carriers require this. I've seen mentions that the Google Fi eSIM requires US towers to activate, but can be moved / reinstalled later without them (didn't test it though).
Just an end user, so don't quote me on this, but I think that requirement was largely a legacy Sprint requirement.
I've purchased newer Pixel devices from my local shop and activated Google Fi just fine overseas. (with the caveat that I might not have all of T-Mobile's bands if I'm back in the US).
