Yeah, but then you can either go for another sweetspot, or up+b onto the stage and either way he can just fsmash again. On the same note, can't pichu DI the throw so the fsmash doesn't hit/doesn't sweetspot? I mean, while the Mario could keep teching...that doesn't mean its not a good/effective way to edgeguard.
Honestly my biggest point was PIchu's recovery > Mario's. That's it. There's not much to dispute. If the pichu lands correctly, there is a 1 frame lag. Pichu can recover from further away and has more options of escaping edgeguarding (in terms of HOW he recovers) than Mario. If anyone is predictable its Mario (easy to hog once you hit him out enough)
Does this really swing the matchup at all? Nah, not really. Pichu will most likely get blastline KO'd is all. But it annoys me when people say a character has NO edge whatso ever. Even matches where Sheik can grab and take a stock off, the character has SOME advantage in some way, it just doesn't counter the chainthrows advantage at all.