You don't know that those vulches would be removed. The score minded would want to hit them as they went wheels up and if they waited too long someone else would shoot first. Shooting them would still be fun for the score minded even if they didn't get points. Does anyone fly for score and not enjoy shooting people down? Do they just force themselves to the unpleasant task for the sake of their score? All you would remove is the score for the vulch. Reducing vulching by that change is just a hope.
Who's speculating now?
Maybe the number is low. But I dont think I'm alone in thinking the number is higher than you suggest. But again I don't have to be right about the number. As as Guppy says, what the harm? Also, I don't mean to hijack JUGglers 'wheels up' idea, but to clarify I'm refereing to a sliding point scale for easy kills vs difficult kills, in which case most 'vulches' would yield few points. If they're fun, or required for a base capture, by all means do it. Not trying to ban picking, vulching, and ganging, just trying to de-incentivise it.