Question about unwrapping a mirrored model

Hi, everyone.

When modeling a completely symmetrical model, is it some kind of taboo to unwrap only one side of the model without applying mirror modifier? I’ve heard that this will mess up normal map, but I didn’t face any trouble with normals when I checked it using simple model. I don’t want any trouble to occur, and I know this is not typical, so I always unwrap whole model, but I’m just wondering :thinking: