What do you mean, IF NH is right? Of course, it's right! Well, I'm convinced. :-)
BMs require peristalsis and that is activated by the continual secession of meals. Once you stop eating, any other activity will be down to the body's need to immediately eliminate something from the bowels so yes, being fairly non-toxic probably makes a big difference.
In my reading from many of the long-experienced fasting supervisors/hygienic doctors, BMs do tend to cease altogether and start again within 3 days after the first meal.
I'm 5'10" but although rakishly thin, I've got a ways to go before reaching skeletal.