Technical Question about Frames (Shun)

I'm trying to figure out a way to ask this where it makes sense. My question involves frame rate differences based on if the hit connects or doesn't. Here is my example:

After KO'ing someone with Shun we all know the best thing to do is drink. Like the back of my hand I know how many drinks I'm going to be able to take depending on how I KO'd my opponent. So, if I KO someone with 3PP I can always get 4DP by going into SOU for 2DP and then taking two more. If I do 3PP and the first P KOs but I still get the 2nd P to come out, I can still get 4DP, but just barely. Basically you see your DP go up on the last frame before the screen changes to replay, which sometimes you can't even see it change until the next round starts, but you always get it.

So after that long setup, here is my question:

As stated above, when the first P of 3PP KOs and the second P connects you still are able to get 4DP. Soooooo, why is it that if the second P doesn't connect you can't get 4DP? It seems like you miss it by 1 frame. In summary are there frame differences for connecting and whiffing moves?

 

It might also be that the game gives stops registering moves based on when the last hit was.