Im blown away.
I've tried to write a reply but I don't even know where to begin... Lets see...
The combination of fan fiction level bullshit followed by "if you don't agree you don't watch or understand hockey." Some serious Dunning–Kruger level shit going on here.
Miller as a center is a black hole defensively. I don't know what the f*** you have watched but even his 99p season he was really bad 5on5 defensively. Then last year he was again crap 5on5 defensively but also stopped scoring and only was able to produce on the PP.
Horvat has got the hard matchups all his time here and he is not great at it (like you said) but he always treaded water. You saw what happened to Miller this year when they tried that with him. He was unplayable. If you remove his name from the back of his jersey he gets sent to the AHL. He got protected 3rd line deployment and EP40 got the matchups. Then Miller did what Horvat did in hard matchups. He just threaded water.
Miller as a winger is a completely different story. He has consistently been a play driver at wing and is very capable filling the far less demanding defensive duties of a winger. Maybe you are mixing the two up in your head?
Oh! And obviously. If you disagree you don't watch or understand hockey!