[albntomat0]

The commenter above specifically says powered on, unlocked. If the phone is locked or powered off, things are much harder.

[hyperpape]

I guess I was confused by "If you shut off your machine", which is not the same thing as locking it.

If cold boot attacks only work against unlocked devices, that makes a lot of sense. But if they work against locked but powered devices, that would be quite possible for LE to exploit in most cases (just carry a battery pack).