The mask is cut, there's no way to argue that it is not. I owned one like that that I melted the bottom of so it looked perfect, but it was still illegal because it was cut.
If a ref noticed, good for him. They didn't, so let it go. I'd much rather they catch the guy with hits on him. Or not one for one me after a marked player lit me up. The small stuff is more than forgiveable.