The symmetry of the staging adds another uncanny element: the frontal camera angles and the identical chairs add on top of the similarity in dress.
And you're right, the similar affect of the two -- the earnestness, the forward posture telegraphing intensity, the lack of humor -- all together, it is off-putting. Later in the interview, Sam leans back which seems to break this unpleasant symmetry.
The poor staging and lighting are responsible for most of what people are reacting negatively to in terms of body language and appearance. Terrible location for an interview for a number of reasons.
They do seem intensely earnest, but both of them always do in the interviews I've seen. I personally don't see that as a negative in this sort of context, however.