>IIRC one of their main thrusts was that over long periods of history, groups of humans have adopted and abandoned stationary agriculture at will, as conditions indicate.
In general they still totally depend on it.
So this would be like saying dogs aren't domesticated, because some left their owners or bit them, or there are groups of stray dogs here and there.
What makes you say they still totally depended on it? I can easily imagine groups of humans having a period of settled agriculture for convenience rather than necessity.