Half a ball is huge
I see it a couple of ways. If the player can run, let's say 4 balls with BIH in 9 ball, but starts running 4.5 to 5 balls on average with the same BIH there is his boost. It typically comes from confidence, practice or training. Sometimes a combination of the 3.
I have seen it many times in APA, especially 9 ball. A lower skilled player gets a little luck or makes a few more balls than the higher player, their confidence is boosted and they get a win. All things considered, the higher skilled player should always win.
I apply it to one pocket more than 9 ball (simply because I like 1 pocket and hate 9 ball). I see guys all the time that can win 9-7 but cannot win 8-8. The difference to me is half a ball. If the same guy has a night where he wins the 8-8 battle, doesn't that mean his game technically improved half a ball (or the opponents game was off half a ball).