It's close enough, because (most of) the encryption keys are wiped from memory every time the device is locked, and this action makes the secure enclave require PIN authentication to release them again.

> It's close enough

Not really, because tools like Cellbrite are more limited with BFU, hence the manual informing LEO to keep (locked) devices charged, amd the countermeasures being iOS forcefully rebooting devices that have been locked for too long.

There is a way now to force BFU from a phone that is turned on, I can't remember the sequence

It’s called restarting the phone.

I believe doing the standard Restart everyone knows is not enough though. The instructions saw were these

Quick-press Volume Up, then Quick-press Volume Down. Hold the side power button until the screen turns black (approx. 10 seconds). Immediately hold both the side button and the Volume Down button for 5 seconds. Release the side button but continue holding the Volume Down button for another 10 seconds. The screen will remain black. If the Apple logo appears, the side button was held too long, and the process must be repeated.

That’s DFU mode. We are talking about BFU in this thread.

Eh? BFU ("before first unlock") is, by definition, the state that a phone is in when it is turned on. There's no need to "force" it.

If you mean forcing an iOS device out of BFU, that's impossible. The device's storage is encrypted using a key derived from the user's passcode. That key is only available once the user has unlocked the device once, using their passcode.