Depending on the particular cannon, in some of them the supervision is active at all times. That his senses just let him see all the layers and through all the layers.
So it's not just that he CAN see all of them all the time. He doesn't even have a choice. It would mean nudity to any degree was extremely unremarkable to the man.
That argument doesn't make sense to me. If you were used to seeing people's bones your whole life, then bones would be part of your model of an attractive woman.
I remember reading a comic as a kid that explained the X-ray vision thing was a bit of a misnomer. The context was that he was going to use it on a pregnant lady in labor, and wanted her consent before he did so and stated the vision wouldn't affect the baby due to some technobable.
I always interpreted it more like he could see in a wide range of the light spectrum and so could just see whatever was already being emitted. Like our eyes but better.
That said, he does have the ability to send out rays from his eyes too so maybe it's more like radar? Not that it needs to make sense anyways....