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That's not the argument being made.
The argument I'm making is that the only MITM/phishing vulnerability is in the initial passkey registration and not in the auth.
So once you have a passkey and the flow supports attestation, as long as you use the passkey you are effectively immune to MITM and phishing.
Now if you input a password or recovery code or whatever and use that to register a new passkey that's initial passkey registration again and not MITM or phishing of the passkey itself. The reason this matters is because you can register as many passkeys as you want. Say you sign up and log in on your phone. Now you register a passkey on the phone. You want to log in on your laptop, use the key from your phone to log in and register one for the laptop as well. Now you lose your phone or your laptop, you use the other to log you in and set up a new passkey for that device.
Once that initial passkey was registered the auth process is pretty watertight and each device you regularly use gets a new key after auth so you generally always have at least one device that you can use to get into your others.
Now of course if you only have one device and it gets destroyed or if all your devices are destroyed in a fire or flood or whatever then you have to go through the untrusted reset/re-registration flow but in all other scenarios you always default to the passkey-based "use another device you own" methods to register new keys.
TLDR: the point is that you very rarely ever do a true cred reset. The flow itself incentivizes multiple passkey auth methods such that bootstrapping new keys from an untrusted environment is rarely if ever required. This works best for "core services" like your email/google acct/apple acct/microsoft acct where you are generally expected to want access to them anywhere you do stuff so the passkey flow is best pared with SSO to increase the odds you've used the acct on at least one other device.
That's not the argument being made.
The argument I'm making is that the only MITM/phishing vulnerability is in the initial passkey registration and not in the auth.
So once you have a passkey and the flow supports attestation, as long as you use the passkey you are effectively immune to MITM and phishing.
Now if you input a password or recovery code or whatever and use that to register a new passkey that's initial passkey registration again and not MITM or phishing of the passkey itself. The reason this matters is because you can register as many passkeys as you want. Say you sign up and log in on your phone. Now you register a passkey on the phone. You want to log in on your laptop, use the key from your phone to log in and register one for the laptop as well. Now you lose your phone or your laptop, you use the other to log you in and set up a new passkey for that device.
Once that initial passkey was registered the auth process is pretty watertight and each device you regularly use gets a new key after auth so you generally always have at least one device that you can use to get into your others.
Now of course if you only have one device and it gets destroyed or if all your devices are destroyed in a fire or flood or whatever then you have to go through the untrusted reset/re-registration flow but in all other scenarios you always default to the passkey-based "use another device you own" methods to register new keys.
TLDR: the point is that you very rarely ever do a true cred reset. The flow itself incentivizes multiple passkey auth methods such that bootstrapping new keys from an untrusted environment is rarely if ever required. This works best for "core services" like your email/google acct/apple acct/microsoft acct where you are generally expected to want access to them anywhere you do stuff so the passkey flow is best pared with SSO to increase the odds you've used the acct on at least one other device.