In what way is it bad advice? To me it makes complete sense. Much of the time when we feel "hunger" we are really just thirsty, so taking a sip of water can be all it takes to satisfy a craving, and stave off snacking. Likewise fruit and nuts are much more healthy than junkfood. So if eating fruit or nuts prevents him from eating junkfood then it is a benefit.

My body fat % is extremely low, but I can't remember the exact number. When I do those electric handheld fat % tests, they error out. I'm an archetypal tall and skinny nerd, basically.

The system works for me because I end up satisfying the craving on healthy stuff before I can get to the unhealthy a lot of the time. That said, everything I write about is based on personal experience and I just try to distill some of the general tips that anyone could use.

I think another subtle thing some might overlook is that you specifically said "serving." That is something like 2 oreo cookies or a handful of baby carrots. It would be a different story if you ate two baby carrots and then half a package of oreos.

Most people would probably make themselves sick before getting too many calories under a reasonable interpretation of this hierarchy.

Quite right. I actually tend to double up my veggie/fruit servings because I like them so much.