Weird artifacts and rotary motion are for all PRACTICAL purposes gone with fast, stacked shutters as in the Nikon Z9. The global shutter's main benefit is flash sync. Grain has nothing to do with global shutter....
Even with a fast readout, PWMing LEDs can still present issues for cameras like the Z9. The global shutter removes that concern entirely with no need for fine-tuning--still need some logic to identify the peak brightness but don't need to fine tune frame rates by fractions of a Hz to reduce banding.
A global shutter has been the holy grail for awhile for cameras like this in wide production. Yes, you can get a machine learning camera with 20 megapixels and a global shutter, but you'll need to strap a whole PC to it to do the data capture. And it'll be manual focus and manual aperture to boot.
Far as I can tell, OP isn't saying that grain has anything to do with global shutter, they're saying that rolling shutter produces artifacts, which unlike other photographic artifacts such as the often pleasant ones produced by film grain, are not at all aesthetically pleasing.
