These messages are generated generically, and just because the proble you hit was this one, doesn't someone else won't hit it for a different reason and have other requirements.  (Note that these messages are *way* better than they used to be, thanks to Benjanmi Peterson's work).

The suggestion of adding that the function takes keyword only argumentgs seems reasonable to me, though I'd have to look at Benjamin's code to make sure it makes sense (I thought it already mentioned what argments/types the function took).  As you say, it is low priority.