My current setup uses Krypt.co (deprecated) to forward most U2F/FIDO2 requests to an app on my phone. The app has some keys stored in my phone's secure secret storage and verifies/signs the request (after unlocking my phone with biometrics or my phone's PIN). This signed response is then used to log into the website.
I believe the goal for Bitwarden would be the same, to allow for seamless login through a secondary device using WebAuthn and friends. Apple and Google are already working on cross-device FIDO2 login support, but for Firefox I haven't seen much announced as of yet. Bitwarden filling in for Apple's/Google's proprietary services would be a way to log in securely without giving up even more security features to browser companies.
I believe the goal for Bitwarden would be the same, to allow for seamless login through a secondary device using WebAuthn and friends. Apple and Google are already working on cross-device FIDO2 login support, but for Firefox I haven't seen much announced as of yet. Bitwarden filling in for Apple's/Google's proprietary services would be a way to log in securely without giving up even more security features to browser companies.