OK... i'm no expert on the saliva thing! But, the mushy foods you mentioned are all carbs... which is the last thing that should be on our plate, not the first thing. Protein first, then veggies, then fruit, then carbs.
I know it doesn't make sense... chew to goo but don't eat goo hahahaha - but it does make a difference, the scientific evidence of it, I don't know how to answer that. But i've tried soft/mushy food even cereal, etc and i'm hungry much sooner than if I eat, say a piece of chicken, or an egg.