Such a generic word. I imagine there are tons of CLI utilities out there with a --passkey option that refer to simply files with a key inside. Kind of crazy that it's being used to mean specifically devices that implement a specific protocol.
Kind of feels like "crypto is a type of currency and not all cryptography", or "SQL Server is a specific product of Microsoft".
Wonder if how it happened this time was people read the specs and explanations of WebAuthn, saw "passkey", never seen that word before and assumed it's only ever been used in the super narrow context of WebAuthn so it can only mean that. Maybe "header" can only ever mean "HTTP header".
Thinking about it like that, it may be more like how "latte" is specifically espresso with milk (it's really just milk), or "queso" is specifically cheese dip (it's really just cheese of any kind), or "masa" is specifically made of corn (it's really just dough of any kind, or it's mass like atomic mass is masa atómica).