Webauthn in iOS fails to set device and goes back to MFA

Authenticating on an ios device and have enabled webauthn. When the user successfully logs in they are asked to “Log in Faster” the user selects either the continue button or the No thanks button but each time they are taken back to the verify MFA SMS process. This keeps happening until Auth0 reaches its limits.
The device is 14.2. The Auth0 supporting documents say webauthn is only supported on 14.5 and above. but why does the Webauthn service get offered to a unsupported device? How do we stop this happening.