During iOS 14 Beta 7 (18A5357e) testing with YubiKey 5 NFC I found Client PIN is only asked in certain conditions.
I was using https://webauthn.io for testing:
Attestation type: Direct
Authenticator Type: Cross platform
User Verification: Required
Register with Resident Key: Required
When I try to register, NFC gesture is ignored and key prompt is only cancellable, no matter if Client PIN is pre-installed on token or not.
If I change User Verification to 'Preferred', NFC gesture is recognized and PIN is asked both during registration and authentication only if Client PIN was pre-installed on token, otherwise is never asked.
*** This bug has been marked as a duplicate of bug 215836 ***