Yeah all the articles I have read on the Qyburn's little birds' rumors are about the amounts of wildfire in Kings Landing. Which makes sense, but my only real question with it is, why couldn't Qyburn go down and see for himself? Who in Kings Landing is talking/knows about the mass amounts of wildfire and is talking about it openly enough for Qyburn's birds to be lead to it? I feel like there are less than a handful of people that know of its possible existence.
The more I think about it, the more I think Cersei should already know about the wildfire. Maybe she doesn't know how much there is though.
I'm curious if the rumors are about something else. Maybe Margery's scheming against the High Sparrow? Maybe something about the High Sparrow's true identity? Maybe something we've not heard anything about yet?