This is the kind of nitpick I'll never understand in comic pieces.
It's a techno organic virus, it's literally grafted to his skin and it makes perfect sense that it has wiring merged into his body parts. It's not a metal cover (like Colossus) and it's not a creative difference, it's what it actually is in the comics. The fact that comic panels most often have it drawn like a generic metallic arm it's just to keep things simple and that comic panels don't have that much detailing going into them, usually, but it's pretty clear what's the techno virus is supposed to look like:
It's the same kind of pointless debate about his eyes. I just finished re-reading Messiah Complex and the way his eyes are drawn is all over the place. I'm posting some examples:
-first twe, he has a white right eye and a normal left eye
-third, normal right eye and light up left eye
-fourth, Cable #24 cover has a normal right eye and a white left eye
I could go on all day but the point is that I don't see why people think that they got the "right way he should be" when actual Marvel drawers didn't even bother to keep such details consistent within the same story arc. I really don't see the point of making an argument about some wiring going into his armpit/forearm or his cybernetic eye being... well, mechanical. Both of which are perfectly fine points in line with the character's look in the comics and the character's background.