You can use the lockdown mode on Android, but you have to remember to turn it on.
Android: Search settings for “Lockdown” and enable “Show lockdown option”
When needed hold the power button and the lockdown option will appear alongside the standard power menu options.
IOS: Hold the Lock button and either volume button to show the power off screen. Cancel out and FaceID will be disabled until you use your pin to unlock the phone.
Not sure about Android but IOS you can actually use FaceID for all the things you want like password managers, log into PayPal, and other biometric features but have it disabled to unlock the phone. It’s what I do, you don’t need to spam anything. Just use a pin to unlock.
I’ve never understood people who are happy to give their biometrics to fucking PayPal and every other random company. Just use a password for everything.