Exactly.
I've nailed the pilot on several occaisons and only got an assist for it. I've also lit guys on fire and didn't get a kill, either.
Spitfires in particular are bad about losing kills against. Their wings are so fragile a half-second burst of .303 fire is enough to knock one off. Because of this, it is almost IMPOSSIBLE to put enough damage into the wings to counter a bunch of 20mm hits to the fuselage that may not have done ANYTHING.
I think type and location of damage SHOULD get weighted, depending on how critical it is. Something like, putting some holes in the fuselage that doesn't do any telling damage is x1, wing hits are x1.75 or x2 or something like that.