Peter Liljedahl
So... From the publications, looks like he uses problem solving, not "having students actually think about math".
You want students think about what exactly if you don't give them an application?
Anyway, thanks, I'm listing his work as evidence supporting my claim.
I mean motivation for why somebody cares about the idea at all, but I think that is less strict so yes. A hole in theory or something emerging from an activity are perfectly fine. But there has to be something there.