In regards to the Urban List program, and suitable seeing/transparency ratings, the only opinion that might actually matter is that of the program coordinator, Terry Trees, as he is the final word on what’s acceptable. The Urban List is one program where conditions, at least sky brightness, is of some importance as the point of the program is to observe objects in light polluted skies.
That said, all of the League coordinators (as one myself, I can report that we actually discuss this sort of thing among ourselves -LOL) recognize that it is all very subjective. My advice is to just pick a method you like and stick with it – no one is going to challenge you on it.
Keep in mind that the primary objective for all of these observing programs is to encourage observers to get out and observe and to have fun doing it. Confession: In my own review of logs for the Planetary Nebula Program, I don’t pay the observer’s assessment of seeing/transparency or sky quality any notice at all. It simply isn’t important. The idea of assigning values to sky conditions is really more for the observer’s use in comparing observations. As long as you are relatively consistent, they might be of some utility in, say, figuring out why you missed a structure that your buddy reported seeing.
The “philosophy” behind having observers report sky conditions is presumably so that a coordinator can compare observations, but if you don’t see the flaw in that position, there is little sense in trying to argue the point.