Well, I never said "orally." If it's beneficial to get NO via sunlight on your skin, it doesn't seem crazy that it might work via some lotion. Even considering oral supplements, one might also take a precursor if the molecule itself isn't stable in the stomach.

It's true there may be some important difference between sunlight-induced NO generation and whatever other supplement/injection/lotion/etc, but my point here is that the right approach is to focus on the mechanism, and avoid the naturalistic fallacy.

Surely you'd need to smear sunlight lotion on your skin if you want to use the existing the dermal route?

Not to mention that one of the premises of the article was that vitamin d levels were a marker, not some singular responsible agent.

The conclusion that vitamin D levels are an effect not a cause came from exploring the mechanisms. And yes, it may turn out that NO similarly is a marker.

It's ironic that the author didn't consider that getting sunlight may similarly be the side effect of the true cause of the stated benefits (being active?).

It may be, but NO itself is also very much a vasodilator, and used therapeutically for that.