The simple fact that it takes longer to improve from a 99 to a 100 vs. a 69 to a 70, doesn't mean that there is a larger on-court advantage to being a 100 vs. 99 over a 70 vs. 69.
So to answer your question, no, I don't believe that there is a great difference between a 100 and a 97, etc, or even a significantly greater difference than it would seem. I do not know this to be a fact, but nothing that I've ever seen would suggest that it is so.