(On the other hand, are we right to casually suffix ngan
to place-names, without including a space? Take the non-coining of
compound nouns as single words as a given before considering
this.)
There are plenty of canon examples of ngan being used in compound nouns. Doing it for a place name that hasn't appeared that way in canon (pItlhberghngan, for example) seems less like a new coinage and more like just an extrapolation from a well-established pattern. (I'd also say the same applies to tej and QeD, though those two have less examples that ngan.)