At first glance it looks like PC creeping in. But a drill instructor isn’t just this harsh bully figure, the flip side is that the health and safety of the recruits are absolutely his responsibility. I have no sympathy if he violated that responsibility.
I don't know too much about the specifics of this case, but I do know that the military is trying to re-calibrate basic training in ways to cut down wash-outs due to preventable injuries. Sports medicine has made major advances in the past 20 years, and the military would be foolhardy not to take advantage of those lessons.