Yea, ssh private keys as well are intended to only stay on Device that generated it. The idea is, that the device you want to connect to has all the puplic keys of all devices you want connect from in their known hosts directory. And you should not transfer private keys.

But of course there is always a battle between convince and security, so there were ways created to transfer encrypted private keys protected with a password.

And the same happened to passkeys.

I myself choose convenience over security in that regard and share my private keys and passkeys on my devices and thus am happy about that development.

The thing is, having options is often good, so a person should be able to choose passkeys in the secure way where you can invoke each device individually and never have the passkey to leave the device where it was generated. To achieve this, website need to allow multiple passkeys to be used, and would be expected from a bank, in my opinion. Maybe they think it is more secure to have just one passkey on one device, which it is, but how do you recover your account if that device dies?