I'm not sure how it's all that different from Windows Hello.

> Passkeys are easy to set up and let you securely sign in to your Google Account using your fingerprint, face, screen lock, or hardware security key. You can create a passkey on this device, or use another device.

When I press [Continue], Windows Security appears where I can then scan my fingerprint which I already use to sign on.

A single glide of my finger worked as expected and a 'Passkey created' screen appeared with [Done] being my only option to continue.

After a sign out, re-enter of my gmail and these are the next few steps: https://imgur.com/a/heLrUkb

It seems like it just integrates the built-in verification methods depending on what device you are on.