Regardless of the outcome, this still looks like a poor demonstration: what's the point of showing how it is done, if you're not following the protocol anyway? My understanding is that those in the room where nuclear experts, so they didn't need a demonstration to know that, the closer the two cores where, the higher the radiation.

Same reason that chemistry professors demonstrate dramatic reactions in front of the class from time to time. It's fun, and keeps things interesting, even if you already know the chemical processes that are happening.