I remember a similar study, even taking into account parking spaces and public restroom stall usage.
We prefer an every-other-one approach, to keep a 'safe' distance, and a small semblance of privacy.
In the waiting room, with several open chairs, if I saw one person with an engaging task, I might sit across so I can see what she is doing, but I would not choose to sit next to her, because it would be obvious that she is utilizing the space.
I know Sheldon in "The Big Bang Theory" has 'his' spot, and even 'his' urinal, but he has been to the ER and other places, and has not fussed about location.
I think the OP was taken off guard and did not have time to formulate words before the wanna-be chair sitter flounced off.