The fact that there was no body language is the joke. The actors were told to sit there as impassionatly as possible.
Meanwhile Ortega is the audience eyes, it is just two people sat there with zero emotion.
Embenga can see a difference as is skilled people person and knows other races but we can't see (future doctors must be more akin to vetenarians knowing hundreds of biological systems not just their own like a current doc)
Then the joke is that while on the outside it looks impassionate to a Vulcan that was a "massive outburst". It's a joke on Vulcan lack of emotion