I've seen them running with stuff missing too, but some listed as non runners are listed that way for the most bizarre reasons.Missing batteries or belts does not make it a non runner, it is simple they put a jumper cable on it and if it starts it is a runner, if not it is a non runner, they are not going to put any more effort into it than that, I have however seen some trucks that a third party has apparently been involved in getting them "fixed up" before sale mostly in CA and then there are a few that third parties are selling outright not requiring a EUC as they have already been through that process.
I have seen several running without belts or even a radiator installed, and many without batteries.
I have a buddy who got his from GP as a non runner. He put two batteries in it, changed the fluids and it fired right up lol