"How far do you want to take that? Any a/c attacked and damaged could be called a kill if it crashed, eventually, even when trying to land back at its base."
Well, if you are forced down into a crash in the midst of being engaged by enemy fighters, that constitutes a pretty clear and reasonable bright line for determining a kill don't you think?
Your example, as stated above, involves an "eventual" crash after hostile engagement has ceased.
Forcing a pilot, in the heat of combat, to crash-land or otherwise set down on your terms, as opposed to his, in a fashion that destroys his plane would clearly constitute a kill.
How about a situation where a plane is engaged by the enemy, shot to hell, goes into an out of control dive, and the pilot at the last moment regains enough control of the aircraft to crash land and destroys the aircraft in the process? No kill?