Are you. Understanding a standard shut down does what you want?
What are you babbling about? Of course, that's why I already said it. Twice.
Both comments I have made in thi thread have mentioned shutting down or restarting the device to put it back into a BFU state.
Since you clearly didn't actually read the comments you are replying to... I'll include the relevant parts from both below:
You can also set it to restart the device if not used within a set time period. Various settings from 10 minutes to 72 hours. So if you haven’t touched your device within that time period, it will shutdown and restart, going back to the more secure BFU (Before First Unlock) state.
Lock it and require the passcode where the decryption key is still in memory because the system is running, or shutdown/restart the device so the decryption key isn’t in memory anymore.
You still didn't answer the question I posed though... before replying in way that seems to indicate you either can't, or refuse to actually read before responding condescendingly.
Since you seem to think there should be another choice instead of doing the same two things to protect the device/data... what would a third option look like? Other than locking and disabling biometrics, or a shutdown/restart putting the device back into BFU mode.
Or are you just stuck thinking a shutdown and reboot are technically different things? Even though that makes no difference here since they both put a device into BFU.