Absolutely did not work for my pikachu. Although I assigned charmander and caught one in a place I haven't seen any before... But that was just like, one charmander, and I walked 10km with him today.
Although, this seems more like just a hell of a coincidence, since this spawns would apply to anyone around you. Maybe try walking with a friend and check if he also gets to catch those gastlys, or if they spawn to you like in a incense (what I think it's highly unlikely).
Also, after the "appraisals update", some "rare" pokemon began to spawn more frequently in places they once didn't spawn before
Edit: A couple of minutes ago, a charmander just appeared where I work. Never seen one here before, even after the "appraisals update".