What’s important to know is that unlike with any other kind of login credential, you do not have ultimate control over your passkeys.

I get where they are coming from, when using the Apple or Google provided storage, but this is just plain false, bordering on misinformation, when generalized like this.

I have full control of all passkeys that I've manually created. They are stored on my physical, usb-security-key. I have some stored in a self-hosted vaultwarden instance. I understand not everyone cares enough to go these routes, but they are possible and part of the standard. They work. Nobody but me controls them. I can give access to others, either by handing them the physical key with the associated pin, or by letting them access them via a vaultwarden account on my instance. Nobody but me controls them.