I'm pretty sure this short was to show the progression of an ODST. It first shows Tarkov, a newbie, at a funeral. He is startled just by the sound of the guns shooting.
Skip past the training to the drop. He is face to face with a Brute, basically about to die. He has some emotion about it, you can tell, but is holding it in, keeping a neutral face.
Now, in kind of a full circle, there is a funeral at the end. I don't think we know who died, since this is obviously farther in the future (Tarkov's hair has grown out a bit, and he just looks older). The blond hair is another newbie ODST; you can see how he jumps when there is an explosion, whereas Tarkov has no emotion about him at all. It's implying that all ODST's start off "human", but eventually get battle-hardened and impassive.
IMHO, at least.