“Rag doll” theory of search warrant.
If police can use your limp uncooperative body to gather information, they don’t need your consent.
And if you’re trying to secure information related to illegal/immoral activity, don’t use biometrics for security.
BTW: pressing the volume-up and sleep buttons together disables Face ID. You can also disable biometrics outright, specify a long complex passcode, and set the device to “brick” after 10 failed attempts. Apple has done everything they can to provide real security if you want it, while also providing the convenience of biometrics if you prefer.