Players like Mango and Armada shouldn't factor into a MU debate, their skill level is too high.
Mango could probably beat a lot of high level Foxes with Link, Armada could probably beat a lot of high level Marths with Young Link.
It's the same as saying Link shouldn't be bottom tier in Smash 64 because of how Isai uses him.
Disagreed with this statement. Just because they play at a high skill level does not mean the mechanics of the game differ for them.
What you can say in a MU guide is that:
Marth/Jiggs MU is very skill-level dependant. Why? At low skill level, the Puff does not have enough options (due to lack of skill, knowledge, etc) to punish the Marth once she gets in. Additionally Marth is probably going to land a lot more high-risk moves, even without tips (also assuming an equally low-skilled Marth).
Alternatively, at a high skill level it's even because Puff has some tough spacing to get around, and when she does get in, she gets more out of it.
What does that tell Puff/Marth players? As you keep getting better, that matchup will appear closer to even.
Mango's Puff is not above this, lol. Nothing about him playing Puff makes this different. Yes, his reads are fantastic... so he's going to get in more. But that has nothing to do with characters.
It's just like talking about PP's and Mango's Marth... do they play Marth well? Yes. Better than M2K? Maybe. Does that make what they do from grabs against Fox optimal? No.
My point is that the player behind the character does not change what they can functionally do. Obviously you could say lower skilled players might not be able to frame perfect this or that, but we are not concerned with that in a MU guide. We're concerned with the theory of what CAN they get out of it... not what WILL they get out of it. When you go into the practical world of PLAYING smash, then you need to use those reads, use that knowledge of "what WILL they do?" That is why top players are top players.