When I say reliable, I mean that the option gets you out of situations better when it lands. Of course most armored moves are unsafe. The fact is, though, they're generally going to be a better option for dealing with your opponents attempts to attack you because they are going to be applicable in more scenarios than a poke could ever be simply because they ignore frame traps for the most part, if not altogether. Hence, more reliable.
Like I said, this game is not only littered with situations where poking not only stops becoming an option, but also contains certain tactics and systematic quirks that do come into play more often than not, and can make using pokes a liability. They do not have the benefit of a reversal mechanic. And again, Quan's d1 is different simply by not possessing anywhere near the same frame advantage a typical d1 will have. It will give him some room, but again, it's not the room other characters get. It's better, but not the option people are making it out to be, and doesn't mask that Quan still doesn't handle being forced to block as well as a vast majority of the cast. Yeah, he can do another d1...that d1 isn't even a guaranteed option. Hell, even without armor, the opponent can backdash out of the next d1. You can't do this with other pokes. It is a purely defensive option that doesn't even give him the same luxury of forcing the opponent to actually have to respect a fast normal he can do. It's a much higher level of conditioning that makes his d1's rewarding levels not as high.
It's simply an area Quan is weaker in than the rest of the cast. He has options for defense without armor, but to say that he is okay on defense is kind of a stretch. He's not, and, outside of Warlock, never will be (that's fine, btw). Armor is a huge chunk of the defense in this game. You can't say that the lack of it is overblown, because it's not. Especially when you watch a Quan get sent to the corner, and just get mauled into oblivion. This doesn't just happen to random Quans. Michaelangelo, Ketchup, King, Dink...it's not something they're immune to just by being good players themselves.
I won't deny Quan might be the best in the game, though. That's how powerful his toolset is. But I don't see how a character like him couldn't have matchups not in his favor. His design just doesn't allow that.