I'm making the assumption that the unoverridden base class _Process() method calls SetProcess(false) and removes the node from the update chain, since there is no need for the node to execute every frame.
I ask this becuase older examples (Godot 3.0) require the user to set the required state in _Ready(), but no mention is made of this requirement in newer documentation.
My target platfrorms have very limited processing power and I don't want to waste any CPU on hundreds of node that don't require updating every frame.