I spent many, many hours arguing with Brawl-haters about the differences in the games. I truly don’t want to get involved with that again, but after reading Sakurai’s quote, it really doesn’t sound like he was confirming that he knew about wavedashing before Melee was released. Instead, it sounds like he’s saying his team found out about wavedashing before production began on Brawl, and they had no problem removing it, because appeasing competitive gamers was not a high priority for them. It actually sounds like he has a negative opinion of wavedashing.
Edit: I guess it depends on which game the ‘development period’ mentioned in the first sentence refers to. Regardless of whether or not it was intentional, it certainly sounds like he grew to dislike wavedashing, since he and his team were so confident in their decision to remove it from Brawl.