I didn’t know what BFU and AFU meant when people talk about phones and I ended up reading this PDF:
https://blogs.dsu.edu/digforce/2023/08/23/bfu-and-afu-lock-states/
It refers to devices that rebooted: modern phones are encrypted and stay encrypted (BFU) until you log in. Then a lot of info is decrypted (AFU).
Thinking about enabling Lockdown mode. Reading about it just makes me think that this is how all devices should work. Have you tried it?
https://support.apple.com/en-gb/105120