I don’t know why you think boys care less about unimportant criteria for a shidduch than do parents.
Regardless, I think it’s very far fetched to say (as I think you’re implying) that the age gap is a product of parental involvement. I think in the litvish yeshiva system, the natural age at which boys are ready to get married is about 22-23, and girls 19-20, and this is the cause of the gap. It has little or nothing to do with parental involvement.