Tested to see if their clothes has that so called glow? I just did and I didnt see a thing. Supposedly you can test to see if you clothes has the "glow" with a black light. I went over everything and not one piece glowed. The white was very bright but that is normal when under a black light. All I was concerned with was my camo and it stayed its dark colored self.
I use All free and Clear and will continue to do so. Its much cheaper.
If somoeone feels I didnt test properly, Let me know!

I've never heard that, but it's interesting. I'll be interested also to hear what others have to say.

What situation is the black light supposed to recreate?

The black light is supposed to test the UV brighteners that clothes pick up from standard detergent (they are used to keep colors and whites bright). Deer can detect the UV brighteners in certain light situations. Most scent free washes will also state that they contain no UV Brighteners. I'm not sure how effectively the black light works, I tried it and couldn't really tell anything. I'd like to hear more though.

Its supposed to show that " glow" on you camo from UV brighteners.

I never heard of a ( test ) for that but I wash my hunting clothes with that Hunters Sport Wash from Wlid Life Researchand then hang them outside to dry.
After that I'll spray that U V Killer on them just to make sure they don't have that glow.
I keep all of my hunting clothes in a sent free bag with some earth sent waffers.

What "glow" could be present if deer are coming to within yrds of my stand?