I like what you wrote and agree with much of it... with one exception...
"garnish is 1) optional and 2) used to help score an entry “up”, not to score it “down”"
I've seen boxes where the bbq was obscured by the garnish. When I have a hard time seeing the meat because of the garnish - that is a negative - and likely to be scored down.
Garnish or not, I don't care but does the garnish enhance or hide the meat?
Sauce or not, I don't care but does the sauce enhance or hide the flavor of the meat?