Hmm, I thought getting the Category excerpts was what it was intended to do. But looking again, you’re correct, it does mention topic excerpts.
I notice arguments are being passed into the function, but I don’t see where they are defined. I have a feeling I’m missing something obvious. It’s a heat wave here and that isn’t helping me think (that’s the excuse I’m sticking to)
One of the arguments is “feed” and I know excerpts are in RSS feeds, so unless there’s some magic happening that crucial bit is missing in the example?
As for getting what you want “in a single request” I guess that will depend on what you want.
Did you already try it?