I will refrain from commentary on Mr. Tuneh's musical performance, but I will comment on his physical performance. As a professional bassist, conductor, and educator I find that level of movement in this setting distracting.
Many have mentioned Joshua Bell or Yo-Yo Ma. I have had the opportunity to play with both of these artists on the stage. They both move when they perform- as a soloist. They also move when they are playing chamber music. I have never seen them play in a chamber orchestra playing a Mozart Divertimento with a conductor, however I would speculate that their level of movement would be appropriate for that piece.
As a conductor, I would find his movement distracting. If I was conducting him, I would feel that he was trying to conduct the group from the bass stand. This is counter-productive to music making. The conductor should be the focal point for the visual aspect and phrasing of music in an orchestral setting, second only by the concert master. From what you can see in the video, the conductor is moving much less, and appropriately for Mozart. Mr. Tuneh looks as if he is playing a Romantic period concerto as a soloist. Playing repeated eighth notes does not require such movement.
As an educator, I would suggest that some movement while playing is good. Internalizing the rhythm through movement is a great way for musicians to play together. However, there are diminishing returns. If one moves too much it can be detrimental because of the extra rhythms that are created in the body. There are many times as a conductor that I see rhythm in the feet or movement in the body that do not match the beat that I am conducting. If your external subdivisions do not match what the rest of the ensemble is counting it can affect the ensemble negatively.
As a bassist, I move when I play. I am also very efficient when I play. I try to move my left hand as little as possible to improve intonation and shifting. There are some times that I heard his fingers slap against the strings so hard I heard it on the video. I would say that he is overplaying this piece. His movement makes playing the bass more difficult. Maybe he is bored with the part? Maybe he is trying not to fall asleep?
I am not judging his playing based on the body movement, but if he was my student I would definitely try to quiet him down. If he was a student level player, his technique would be affected by the extra motion of spinning the bass to and fro.
Respectfully,