You are correct but from lawyer perspective (IANAL btw) it is important they use the word "believe". As I was explained by a friend who is attorney, if you never had experience with certain law, like in this case perhaps never been subpoena for records by US, then you have a right to say you "believe" something is not the case. This is still not deceiving statement. But the moment you have been proven wrong by US Gov for example, your claim would have to be removed.

on FastMail alone I did not like how slow it is. I was testing them and Protonmail at the same time and was very impress how simple it is to setup my multiple domains/users on Proton and how fast encryption/decryption works. And Protonmail "[...] is outside of US and EU jurisdiction, only a court order from the Cantonal Court of Geneva or the Swiss Federal Supreme Court can compel us to release the extremely limited user information we have.[...] [1]

https://protonmail.com/security-details

Full disclosure: I don't work for Proton; I'm just their happy mailer :)

EDIT: Slow I mean their GUI comparing to Proton. It might be more the number of extensions I have to block or limit different shenanigans such as AdBlock etc.. but needless to say, Proton does not have that problem.