Is there any difference in the individual conductor insulation of UF and NMB ?
I do not know if there is a difference except for the outer jacket.
I want the wire makers to sell spools of THWN with black, white, green twisted together so they are like a little triplex. That would be nice for small pipe jobs.
After reading Bob's comment it hit me that it's probably just the ground they are worried about in NMB so it can't be used in wet locations. It's not insulated.
If they made a type of cable with an insulated ground that would probably solve the problem and an outer covering that was sunlight resistant or we could just use UF cable.
The only problem with having black,white and green on a spool is that some people would complain about ahving to pull a ground ( waste money ) in EMT.
No kidding the multi-color spools sound like a good idea . I would probably try it to see how it worked out. And we could have another spool of black, white, red and green, and another spool of black, red, blue, white and green. And then someone would figure out that it was easier just to go back to having all the cable on sperate spools.