This issue has persisted since Forza Motorsport 3, though it was amplified in Motorsport 5 for no particular reason. The Enkei NT03+M wheels are ridiculously inaccurate. The highest LOD model seems to be modeled for the smallest possible wheel size. Lower LOD models, however, are much closer to the correct shape, but they’re all very low quality.
Here is the impact of these wheels at size of 18" on a car.
Real life examples
Considering that Work X JDM Concept GT5 wheels recieved a model change early into the game’s life, I believe these inaccurate wheels, as well as all others, can be fixed too.