It is. This is self-reporting, so usually you have people overestimating how much sleep they get. The absolute difference does not look that dramatic, but I would suspect that in reality it's.... Well, 30 minutes of sleep is significant, so if it translates to 20 to 30 minutes and that's an underestimate of what really happens, you're thinking about a significant sleep loss during deployment.
On November 26th, 2013. See this statement in context.