Please explain Rakuten Securities Passkey system

I consider myself decently tech literate, but I'd like to better understand the new passkey log-in system that Rakuten Securities just introduced.

I setup the passkey login and if I use my Android phone to sign-in, it works fine – I just need to use my fingerprint.
However, on PC (I use Win11) I get a Windows pop-up window that gives me the option to authentificate the passkey with my Android phone, but I need to connect it via bluetooth.
With my current setup it works, but I wonder what happens if I want to login from a different PC, especially one that doesn't have bluetooth built in. How would that work?

by Iekei_ramen