It is certain that the group from 'Revenant' did not become standard borg - their behaviour is significantly different from the main collective's.
Of course, they did not remain "basically the same as they were, psychologically, only united in the mini-collective, without wanting to assimilate anyone further".
They still felt that hunger.
But it's also true that their main objective (which appears to be even above assimilation) - revenge - would be instantly qualified as 'irrelevant' by the main collective.
And their unusually pacifist behaviour from the end is further proof of their uniqueness.
In my opinion, making this mini-branch of the collective exhibit a behaviour different from the borg proper (perhaps more ambiguous, morally-wise, than the pitch-black borg) has much more potential - essentially, is more interesting - story-wise.
Well, they certainly are going to be different, but the question is how exactly. I will assume that whoever contracted Carson and planned the whole thing (possibly Section 31) was not a complete idiot, and that - if they actually planned to create the Borg they could use as a weapon - they had or thought they had some means to control them/use them, to an extent at least - which would mean making them different from the regular Borg, I presume. Which might not really work, but it would be interesting to see it clash with their desire for revenge... In any case, it would be great to see what happened with them later on.
I have a question about something I don't understand - who or what was it that attacked and assimilated Harlow? Was one of the Borg drones still alive - and if it was, why didn't we see it afterwards? The way it was depicted in the story, it seemed almost like it was the ship itself or some sort of mysterious force. But who/what was it, really?
I also liked that Marc D. Giller used Locarno, although I sort of was hoping he wouldn't even have mention the events of "First Duty" directly, just to be even more subtle with his inclusion.
I disagree. Trek lit writers should not assume they write for the audience that already has the knowledge about the canon background from the TV shows and movies, even if that's the case for the majority of the readers. Any literary work should be able to stand on its own. The story should be understood by a potential reader who hasn't seen the episodes where the characters originated from (in this case, TNG "First Duty") or doesn't remember them anymore, rather than just the people who have re-watched every Trek show several times or regularly visit Memory Alpha and Memory Beta.