ZeRo's comment about Kirby having a good neutral threw me off too, but I realized something when he followed that with "Kirby is bad at approaching."
I feel like often when people discuss neutral in Smash Bros, they translate it to "how well does this character approach?" But that's not the only element of neutral. It's about having all of your tools available to you and jockeying for position. ZeRo mentions that Kirby can force approaches, so it becomes a matter of how well can Kirby maintain a percent lead, or get one back if he has the opportunity. And because Kirby does so much damage every time he gets in, while he might have trouble approaching, his ability to even out the damage is quite good, which then forces the approach back on the opponent.
I also sometimes wonder if ZeRo is so good at winning in neutral that it colors his perception of some characters. What I mean is that he rates characters like Dedede higher than one might expect, yet we talk about how slow and bad Dedede is all the time because of how hard it is for him to get things going. But someone like ZeRo has the skill to consistently win neutral even with worse characters, so it being a weakness might not be as pronounced to him.
Given the discussion about Ven's matchup chart, I do think people have a tendency to unfairly rate low tiers and just assume that their character wins a particular low tier matchup. I'm not going to say that Zelda beats or even goes 50/50 with Cloud necessarily, but my first thought when seeing that was wondering what about Zelda's properties would even make someone think Cloud is an even matchup. The first thing that came to mind was Zelda's dair, a move that lasts a whopping 11 frames. Sure, most of that is the weak hitbox, but it's Cloud. You don't need an especially powerful attack to mess with his recovery. Moreover, Zelda doesn't have that hard of a time getting an opponent offstage, because of powerful tilts, a Bowser-esque grab, and decent throws for creating distance. Combined with the fact that Nayru's Love just outright beats a lot of things, I could see what Zelda could do to Clouds.