Oh yeah, I also agree n believe that's the reason. Although having a key active does not mean the super secure government level threat protection, if one activates that threat from state protection, many of the account recovery options become unavailable.
I assume the number of account recovery options diminish with increasing levels of protection.
I have a security key active but it still offers to send me an SMS code for some reason (worryingly, to a phone number I no longer have... should probably get on to changing that)
I assume the number of account recovery options diminish with increasing levels of protection.