Incident meters are designed to measure the light that the camera will be able to see and give you a camera setting, to do that you have to point the dome at the lens. If there was a gray card in the scene it should expose as expected at zone 5. Skin tones, any, should fall appropriately also.
When you point the dome a different direction all bets are off.
Having the highlights blow is a different problem. You may want to measure that so that you can decide how to develop the film but in most cases with negatives, that's not a big concern.