More detailed information about the “plugin passkey provider integration” is available here:
From an initial read, the main functionality is that this allows Windows Hello (biometrics or PIN) to be used for user verification when using passkeys stored in a third-party password manager. It is not clear whether passkeys that were created and verified using Windows Hello on one device will be usable on any other device (the passkeys themselves may be syncable, but the biometric data used by Windows Hello will always stay on the local device).
It will be interesting to see if Bitwarden will try to use this integration (as opposed to developing their own user verification functionality). IMO, it is essential for any user verification method used by Bitwarden to be syncable.