Yeah, but don't forget the car has to be within the grid spot to even initiate a valid start procedure. It would allow them a few cm forward movement between the green flag and the lights going off, which lasts circa 10 seconds. That's almost completely irrelevant. And the starts have been like this for decades and Bottas is not the first driver who jumped the start, so if gaining an advantage would be possible with slow forward movement, they would be doing it already.
Of course, I'm really just playing thought games here. But I could imagine having the driver stop the car as far back inside the grid spot as possible and setting up the clutch to give the car a minimal "nudge" when released just a bit, like 1/5th or so. The driver would do this when the last red light lights up, not directly after the green flag. So the car starts to move between 5th red light and lights out, after which the driver completely releases the clutch and starts with an already (if ever so slightly) moving car. Or maybe this is all way too James Bond Q-Technology thinking on my end. We'll see.