I think you're wrong about that. Very small percentage differences in DNA can have massive biological consequences. The percentage difference is almost irrelevant. For an analogy, I can change one line of code in a 500,000-line program and change it from a functioning Bitcoin node into a program that displays a picture of Donald Trump with a cat on his head.
Discussion
The point is your byass (and mine too). As I said in another response to you, I absolutely do disagree with your fundamentals.
Natural behavior in large numbers of species (and even subspecies) is very, very finely tuned to avoid matings outside the group. The main tendency of Life is divergence. Exceptions don't disprove this.