There are lots of examples of just how unpredictable the result of any two particular moves will interact with each other in fighting games. Say, for example, Dhalsim’s mid kick drill vs. Honda’s headbutt, even in a relatively simple version like ST. What happens? Sometimes the drill wins. Sometimes, the headbutt wins. Sometimes they trade.
Sometimes right after a match, you wonder what went wrong because it’s not so clear in such cases- did you have the wrong counter move, or did you just mistime it? Sometimes, you DO know the counter, but are led to believe it is NOT the right counter, because you mistimed it (due to pressure, mis-Executed, etc).
It’d be nice to be able to replay your game, but starting from just before the critical points (e.g. where your counter missed or did not work as you had hoped during the match). You could play it from that point in time of the match (that particular state), over and over, for about 5 seconds each time until you time it right (or, experiment with different counter moves).
I think GGPO uses particular game save states and syncs them up, eg it starts both players off at the select screen with a certain number of credits for each. So it can start from a particular state of a game- with the same exact pixel perfect distance and recovery times etc each time. It could just start you off from the point you want each time, put you right in the flow and let you get used to that particular situation, exactly as it happened.
With the Dhalsim’s drill vs. Honda’s headbutt example, you have control over Executing your own move’s/counter’s timing, and best guess of your opponent’s next move and his particular timing, but even when you guess RIGHT about both it is still easy to trade or even get hit by it.