(this is sort of off topic)
236[A] is not good for him at all. It's very hard for him to get out against a good W.Len player, and you're bunker cancelling a projectile so you're bound to get your ass beat for doing that. Throw in that W.Len can simply just keep her assault aerial while Kouma is in there to prevent any bara'd EX Dunks and it becomes hard for him because a lot of his escapes get shut down.
You have to keep in mind that this is at each character's full known potential. For example, Kouma is 4.63 vs. V.Sion. Normally a V.Sion player wouldn't be that much of a problem for him....at an American level of play. Because V.Sion isn't great at escaping either, she usually has to just block out whatever gets thrown out at her. What does Kouma, a grappler, want you to do? He wants you to block. However at a japanese level of play, critical stuff like this is taken into account and both characters are playing according to the matchup, and one of them is getting more bang for their buck in doing so.