Which still results in a clearly weaker defense compared to not persisting data, as the data will remain available to be acquired legally or illegally even after powering the system down.
But a motivated nation state can size servers without powering them down, it has been done in the past. Sure, it's harder than just smashing the door and grabbing them, but still possible. In the end, when discussing security one has always to start by clearly defining the intended threat model.