Also, what's stopping us from falling into the passkey version of the world we got with OpenID, where many services force you to log in with your BigTech account?
Facebook is still going to want me on their websites even if I’m running Firefox. Most websites people visit will not do any chrome WEI attestation. Likely exceptions are sites which handle any legal, financial, or health-related data. Not credit cards. I doubt most Google properties will use WEI.
They still want to slurp up all my juicy Firefox usage data and I bet they think a lot of such users will drop their services like a rock if it meant otherwise dropping their browser.
Or at least they will at some point in the near future.