Those are concave wheels so that's why. To get concavity, they drop the center lower so the spokes can come in. If you get high offset so it doesn't rub, there is very little backpad so the wheel center is very close to the axle.
You can have the mechanic shave the threads since they're on the end and not used, just make sure he cleans it up. Or you could run a small spacer. 4 threads is ~5mm.
If I didn't run big spacers, my center caps wouldn't clear on the rear of my car either.