That said, I was wondering if it is "allowed" to connect your black water hose to the RV site water spigot to flush/drain your black water tank?

It would seem to me that would be a bad thing.  I would think you would only want a potable water hose to be connected to any spigot where someone may drink from...but then you would also not want your potable hose connected to your black water flush valve either (I have the Rhino one that is right on the flush hose).

Can someone school me on this?  I don't drink my RV water regardless, but some may.  I think I already know the answer, but I just don't recall seeing this noted anywhere.

The risk of contamination is minimal as there is an anti-backflow device with an air gap so it would likely be safe. However, I still would not like the idea of connecting my drinking water hose to a faucet to which someone had connected a hose used for black water flushing. It isn't that I think the tank's water would be contaminating the hose, but the dirty hands of someone handling sewage hose and flush hose wihtout sanitizing between handling them. In that case, a bottle of bleach is a good thing to carry along and sanitize the faucet before connecting.

I was at an RV park in Kentucky where the sewage drain was close to the fresh water faucet. The kicker was that the fresh water faucet was recessed into the ground. When we got there, it had been raining heavily and the recess for the faucet was flooded. The next day after the rain had stopped and the water had drained from the recess, I definitely used a good amount of bleach on that faucet before connecting my hose to it. That was probably the worst setup for water and sewer of any place we have stayed. It was done so the park could be open year-round. Better would have been freeze-proof stand pipes. Then the fresh water faucet would have been above the level of the sewage connection instead of below it.

Exactly! Minimal risk and likely safe. Backflow preventers can fail, or there could be cross contamination via airborne microbes. And yep there are many RV'ers who connect their fresh and flush lines with a Y and don't have problems. But since its totally unnecessary anyway, why do it? 

BTW, if there aren't backflow preventers at each campsite at the place with the recessed faucets the whole water system could get contaminated by a flooding rain like that. All it would take is a loss of water pressure and an open submerged faucet. One more reason for me to never drink or brush my teeth with my tank water....