I must admit I thought it was clear but obviously not. Yes a grounding makes a ball dead. But in this context there is doubt. In other situations such as held up, maul driven into touch, pileup, etc, I am suggesting that there is no doubt. (Even as it has been pointed out, attacking foot in touch or even an attacking knock-on - there is no doubt.) Doubt = scrum - attacking ball/side going forward before doubt. - Anywhere on pitch.