Invalid AuthenticatorAttachment information in authentication response during cross-device authentication

Scenario

1. Use Safari browser on macOS and trigger Webauthn authentication
2. Select QR code authentication flows
3. Use Android phone's passkey (with play service beta) and scan the QR code
4. Perform UV on Android device
5. Check the authentication response coming from the Safari on macOS

Issue The authenticatorAttachment in the response is "platform".

Expected behavior The authenticatorAttachment should be "cross-platfrom". According to the spec (https://w3c.github.io/webauthn/#dom-publickeycredential-authenticatorattachment), the value should be "cross-platform" since the attachment modality at the time of authenitcation is "cross-platfrom" rather than "platform". Without "cross-platform", RP cannot decide and guide for the user to register the "platform" authenticator on the macOS.

I just checked this issue with Safari (16.2) on macOS (13.1). Also, you can refer related issue on the fido-dev-group: https://groups.google.com/a/fidoalliance.org/g/fido-dev/c/XvDWBH6PhQ0