The good news is that this feeder has agreed to go up and take a look (while insisting that his cats are not the ones going up). I pointed out that I agreed that in all likelihood they are pet cats. It is a good idea to look into the situation before it flares up for example. If you know there are pet cats running around upstairs, it's a good idea to look into it even before some complains, because chances are it's just a matter of time before someone DOES complain.
You might be one of the lucky few whose neighbours all don't mind a cat running around, but the majority of people will find that their neighbours DO mind, or that they mind when the cat defecates. Knowing about the situation early means that it is possible to intervene before the complaint goes to the Town Council.