This is actually for all non Chalcedonian churches not just the Coptic church... I don't know how you say that it's just one nature "Man-God" or the divined man as saint Cyril of Alexandria I think put it, but when it comes to answering people who ask about how Jesus said "The father is greater than me" you say that Jesus was talking with his human form (his human part) I mean saint Cyril (I am not sure again) said we can't speak of two natures after the union, after the incarnation we can't speak about two natures... I think this is a contradiction, and it bugged me for years.
Plus how it can be one nature of two natures without mixture or so, this is not logical... and don't mention the example of the steel that is in fire, the steel that is in fire becomes molten steel and some of its properties change (like being solid, or the color when it becomes red, maybe even the outer layers turning to ash) so the steel in fire example is not logical for me!
By the way, I'm kinda agnostic, but I like to know about theological arguments and so... I was raised a Coptic orthodox and since I was 16 years old (7 years ago) I swayed to many religions but stayed for some time in a protestant church and now I left (or thinking about leaving) again, so yea my knowledge is not great and I apologize if I couldn't make my question clear enough.