I love how professionals who work at that facility and have probably deeply understood those principles for decades still display so much wonder at seeing this experiment with their own eyes.
My guess is that it's a standard demonstration for visiting dignitaries and the like.
They are used to the chamber and with experiments in the chamber, but this simple experiment with a feather and a iron ball is very different from what they usually see.
They probably usually see only heavy objects and mechanisms for space projects being tested there. Such a graphic and basic experiment must be well outside the norm.
Why do you say that? They could have easily made the apparatus for this experiment.
Now, they are recreating an experiment last performed at this scale on the moon. It's an unusual break from the norm, and I'm sure half of their grins were the phenomenal waste of power to perform such a silly experiment. (Seriously, that chamber was hauled down to a couple torr in three zarking hours!) Professionally goofing off is immensely fun.
(Tiddlywinks with a forklift would be another, and there was a guy who used the armor coating a Blackbird uses in a robot wars competition.)