Anyways, I am not going to put that much analysis into the text but into the implications (and byproducts) of the text. The text enough is clear of its message: the fear of smaller species getting annihilated by less friendlier forces.
Here I want to say that this is actually the conscious message, for which the unconscious reflection is the fear of the unknown (the great trope). This implication is rather amusing that they, who wants them to be isolationist, would not include them into their dominion in spite of cracking the language, speaking it perfectly, being able to send it back somehow safely and not even telling them how to be technologically advanced. While they may have factored for curiosity, they didn't factor in the possibility of future-proofing - a mistake they made and will learn to not do so again when they see Earth.
Yet maybe, their reason for not doing so maybe due to the fear of seeing their past being reflected back on the Terrans. For which, the narcissistic self-help to their other is clear, but, withal with that unconscious quality, the conscious quality truly is sincere. And this narcissism could've came from somewhere else, where they were told to not do these dangerous messages and where in similar climes. So much we could know, but only can speculate on.
I shall however keep quiet on the hierarchy part, I will only blurb this: their space economy enforced their current Superstructure.
I think your analysis of social organization is wonderful. You think in systematic terms.
My plan for this story was a little more diabolical: in my original version (which my son talked me out of) Leader 1 incinerates the record and has the trash teams going out endlessly looking for another, although he knows they will never find one--or at least he believes they never will.
If I develop the story it will be a commentary on hierarchy, power, ideology and competition. So.... you really did get the drift of where I wanted to take it.