I’m pretty sure this has to do with Inform’s treatment of indistinguishable things. If there is more than one thing (or object, I guess) with identical dictionary word entries, Inform assumes* that the player has no way to refer to one of them rather than the other, and so it will group them together in lists, refuse to disambiguate them, etc. That’s why if you write
A coin is a kind of thing. Lab is a room. There are five coins in Lab.you will get “You can see five coins here” and when you “take coin” you will not be asked “Which do you mean, the coin, the coin, the coin, the coin, or the coin?” zarf explains that here.
So making the things/objects privately-named makes them indistinguishable to the parser, and that makes Inform assume the differences among them aren’t important, so–at least in some cases of the list-writer–it lists them as “three frobs” instead of giving their names. (Here is a place that I mention that this affects the list writer, though presumably somebody else told me that sometime–I can’t find where.)
A workaround is to give them internal names that the parser can understand. If the player can type an unobvious name like frob1 or frob2 and be understood, that’s usually not harmful to their experience! But whether this works would depend on the specific reason you want them to be privately-named.
*“assumes” because there are some cases involving understanding by relations where the player would be able to distinguish them, but this mechanic doesn’t catch those.