Yes, because as his example showed, a match against Falcon was exactly the same as a match against Ganon, a Falcon clone.
It wasn't stale. And, even to that extent, the game engine allowed for more excitement regardless of the moves to which some of the characters used. Had the game been just Fox, it would have been more exciting than almost anything Brawl. Yes, it would have repeat after repeat of matches, but the gameplay that results from Fox dittos is crazy fast, technical, and full of mind games.
Even if there were a handful of characters that were clones, how many played exactly the same? There was Fox and Falco. They were both high tiered but for two completely different reasons. Mario and Doc. These are the closest to actual clones in the game, but there are slight differences which gave doc a noticeable advantage. Ganon and Falcon. That difference is painfully obvious. Link and Young Link. They both are little spammy whores, but one of them is much, much better at it. Marth and Roy? Woooooowwww. Pichu and Pika chu. Pichu was everything Pikachu was, but 20X worse for some reason.