This ending is the emotional payoff prepared by the documentary film style showing this captain managing the crisis on his ship in his by-the-book manner, because he was the leader he needed to be in that situation. After it was over he could finally let his guard down. That flood of emotions also triggered a release in the audience.
I purchased an Edge of Tomorrow blu-ray after reading a long appreciation thread on twitter that made me want to watch it again. Last night I paused watching, because of bedtime, after Emily's death scene at the French farmhouse when you realize Tom has evolved from an unlikable jerk to a likable hero. You see it in his face when he said, "I wish I didn't know you." That quiet, sad interlude was a nice tonal break from all the action that came before.