Surely there's a point in any tackle when it becomes "an unavoidable coming together"? Seems like another line that's drawn subjectively based on whomever is refereeing on that day.
I think it's because it's still seemingly used by referees too. Just look at Doku on Mac Allister. Doku touches the ball slightly (and I mean slightly) and kicks Mac Allister in the midriff with his follow-through. A clear foul not given because "he got the ball"
That said, I agree with your...