In vaultwarden, they do appear in the web client. The behavior you're describing hints that your passkeys are not being stored in bitwarden.

...and tbh, the UX sucks pretty bad: I was trying to store a passkey in bitwarden, but it was failing (unrelated networking error). I had two options: add it to bitwarden (which failed) or cancel. I hit cancel and was prompted for my fingerprint, which I provided -- this ended up storing it on my device... no input, no description of what it was doing. The website came back with "passkey now enabled" :facepalm: