This team building exercise probably lasted for 2 days or so. And you saw a highly edited version and are focusing on a specific scene-- as a contrasting example, they looked more than sufficiently bought in when cheering Graves for leading the group exercise successfully. In the scenes where they looked sullen, I am sure the drill sergeant expected them to look very serious and attentive; this is like saying a class listening to a lecture is sullen and not buying in. Also, the most sullen looking scene seems to have shot right after the swimming pool task; from the looks of it, many of the players were not good swimmers, so it was probably particularly demanding and stressful. So, the Lvs were likely exhausted not "sullen."
But by all means, take any opportunity to assume the worst about these student-athletes.
These kind of team building exercises are very commonplace, in the corporate world as well as in the realm of sports psychology, that I am not surprised that Holly would pursue this route.
At the time, I thought, well if this event improves communication and helps some players feel more comfortable in stepping into a leadership role, there might be some incremental benefit. In hindsight, this seems to have been a poor use of training time. But would the LVs be doing better, if they had spent these 2 or three days working on jump shots? I am not sure that would have made much difference either but we will never know I suppose.