1. This doesn't necessarily mean it was purposely programmed to be that. Just like the Infinite Dimension Cape glitch wasn't purposely programmed to be that.
Can you perhaps source something that truly indicates that Sakurai did this?
I don't know of any articles with it, but at the very least DACG was purposely programmed in (it was in Melee as well), and at least from what I've heard from the P:M developers, DACUS was very deliberately programmed in, like, it couldn't have been a mistake.
Similar to how l-cancelling (or "smooth landing") was very deliberately programmed into 64 and Melee.
It really depends on your outlook on the word "glitch" imo. Sakurai didn't intend wavedashing to be in Melee, but they found it, and didn't bother fixing it because they were on a tight schedule. I think it's up to the individual to decide whether it's a glitch, but knowing that Wavedashing wasn't meant to be in Melee in the first place is a good start.
Well I mean, while he may not have planned for it to be in the game, after it was found, they purposely left it in, in other words, they intended for it to be in the game -_-, at that point it's a feature.
And even if they didn't find wavedashing/wavelanding during development, saying that it's a glitch is as silly as saying any tactic, such as shine>bair a glitch. The codes are working exactly as they were intended.
Maybe it's one of those things he wanted people to find out, like how if you hit Starfy enough, he rages and hits you with ridiculous (it's like 3 seconds lol) hitlag, damage and knockback.
I've never heard of that, lol that's cool.