Passkey is some sort of specific unique key to a device allowing to use a pin on a device instead of the password. But which won't work on another device.
Now I don't know if that key can be stolen or not, or if it's really more secure or not, as people have really unsecure pins.
That's a terrible take … He's confusing "what it does and how it works" with "how you manage it".
It's like saying "don't call it a password if you write it down". It's confusing and unhelpful.
No it's literally in the spec. Passkeys are designed for cross device synchronization. You have to go out of your way to make it local only (or use a different webauthn spec like physical security keys)
They're just private keys. By nature you can copy them wherever you want. I guess I don't know why he's making that distinction at all.
The original spec is resident keys including TPM protected or hardware token protected keys designed to be impossible to copy. That's why there's a distinction.