It seems to me that is a variation of the same idea. The only difference is that nomadic groups need access to much more land in order to generate the same number of calories that agriculture does.

Well, agriculturalists before the modern era were generally more malnourished than hunter-gatherers. Mostly due to a lack of various nutrients and heightened risk of famine due to low food diversity- one drought or blight can wipe out your whole monocrop, leaving no backups or alternatives. Hunter gatherers sampled a much broader swath of the ecosystem, so one food source crashing for a year or so had a much smaller effect.

And yet it's the agriculturists who are desperate for land.