Not parent but are you saying wiping it doesn't stop it phoning home to report Find My Mac location for the previous installation?

That's.. entirely good I suppose, but would be news to me.

Its more than that, You can't wipe it at all until you log in with the apple account it was connected to. Rendering a stolen laptop effectively bricked and only useful for parts.

That's not necessarily true. There is a permanent vuln embedded in the T2 chip. If you have a locked laptop, getting past the lock is possible.

Is that new with Big Sur? I wiped and reinstalled at the weekend (preparatory to upgrading) just by holding CMD+r on boot > disk utility > format.

I think its any macbook that has a T2 chip which only came out somewhat recently I think.