I think it generally makes sense. It would be hard to implement it any other way within the gameplay.
I also have some more philosophical thoughts on it though:
One could ascribe ethoses to various hive minds in fiction but I've always seen the ethoses in Stellaris as values, not descriptions. They are things the society/government/people in question consciously aspires to. I think it is hard to imagine a hive mind that evolved naturally aspiring to these values. There are a few reasons for this and they're all tied to the role of language in providing a space for communicating the struggle between these values.
A naturally evolved hive mind would have no need of language, in the broadest sense – the manipulation of symbols to attempt to communicate meaning. They don't experience alienation from other people in the way that we do. I use these letters to talk here because I cannot know what is in your mind, and you cannot know what is in mine. A hive always knows what it thinks.
Additionally these ethoses are based on one of the fundamental structures of our text-based cultures: Binaries. Meaning in language is predicated on a series of relatives, often binary at the base. In systems of meaning A = A because A ≠ B. For a concrete example, Militarist is functionally the same as saying 'not pacifist'. While other positions exist as a signifier it attempts to be everything its other isn't. Accordingly, a society can only be dominated by people aspiring to be militarist if pacifists exist, if pacifism is an intelligible position within a symbolic system predicated on the alienation of one from the other. A system of discourses (by which I mean patterns of knowledges) that values Militarism can only exist through denigrating Pacifism, and for this to be the case there must be an irresolvable gap between the people holding these positions.
No such gap can exist between the embodied positions of a hive. They have no Other within their own culture. As a result it is hard to imagine this kind of struggle going on in the hive minds Stellaris seems to want to portray. In a species that evolved as a single mind, and as the sole intelligent culture of its planet there would be no ideological struggle, it would be nearly impossible for them to conceive of themselves in the terms given in the ethoses. They're too alien. The Geth could manage it but they're a rather odd example... a sort of bottom-up hive formed of overlapping contingent networks rather than a fundamental link. Additionally the Geth are anomalous because they are software made by a non-hive mind species. They carry the biases and some of the situated knowledge of their creators to some extent. They are a textual culture because they were designed to be understood by a textual culture. An evolved hive has had no such considerations built into its development.
It is possible that a hive could come to see itself through these ethoses via its interaction with other cultures once it is spaceborne, but I think that implies a structural compatibility between the psychology of hives and other species that may not exist. Once learning to speak – in order to try to overcome their alienation from other species – they become their own master signifier, their own anchor of meaning, everything would be processed through the knowledge that they are a hive. They would now have an other but a radically external Other. While Militarism is forever tainted by an element of Pacifism within it, the hive contains nothing of other species within it – therefore the opposition it constructs isn't textual.
In other words, an ethos is an aspiration, an aspiration is an image we have of what we want to be. The desire to do this is in part the result of the alienation that is partially the result of, and partially the cause of, language. We have to imagine others because we cannot know them (and therefore need language to communicate), and we have to have an imaginary version of ourselves because we cannot know the whole of our self (because language is never our own, it places a piece of other within us, reproducing our alienation with other within ourselves).
The hive has no other and so needs no language, as a result it always knows itself and so it has no reason to imagine itself as anything other than what it already is. When it does have to learn language it either finds some way of maintaining its position, retaining its radical distance from other species' somehow. Or the experience of learning to communicate with other species' is highly traumatic potentially leading to a psychotic break caused by the breakdown of its Self. The latter option would obviously be inconvenient for gameplay
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