It’s pretty well established that any biometric can just be taken from you — facial recognition is super easy and it won’t be hard to force your thumb onto the sensor.
This is also the case for things like blood draw for blood alcohol testing.
The only unlock key that’s (probably) truly yours is something inside your brain.
I’ve mulled/wished for this for years. Also useful at borders, where in the past I have actually been asked (required) to unlock phones and laptops. Generally you have no rights whatsoever there.
Those shadow accounts would need to be ‘lived in’ to pass those border checks. My worst experience was traveling with new, obviously burner devices — border agents were extremely suspicious.
Virtually every international border on the planet.