Hey! gonna try to look for it, but I'm not sure if I saved that one...
However, Godot's optimization and good enough hardware can definitely run the "slow" version at very high fps, this implementation is more impactful on lower-end hardware.
There's also a possibility that the engine itself made several optimizations under the hood, but I'm not 100% sure about that. Still, for simple bullet hell games a moving node2d may be enough, but when there are a lot of things happening at once on the scene, the lower memory footprint each element has the better~