To be honest I don't really agree with the assessment that Dark Urge is not an origin character; it is.
I don't really give any credence to what Larian define a 'Origin Character' as - their ability to define things accurately and then be consistent about that is sketchy to poor and extremely unreliable at best. What they say doesn't matter - what matters is what is actually the case.
What is actually the case is that Dark Urge is an Origin Character with a few minor differences to the other Origin characters - namely, they aren't immediately available for recruitment if you don't play as them, and you can customise their appearance and class details. That's it. To say that Dark Urge is just a tag is a hair split - because if you can say that - "It's just a tag that gets applied with your other tags, and opens up extra dialogues, story elements, interactions and so on" then you can apply that equally strongly to, say, Shadowheart: Shadowheart is 'just a tag' that opens up extra dialogues, scenes and content in exactly the same manner.
To back-quote the Larian Origin Character FAQ:
"[The Dark Urge is a] pre-designed character. You can select them during character creation to start your adventure in their shoes (not available during Early Access, but will be added at launch) [...]. The Dark Urge comes with personal backstory, quests and motivations, and has unique ways of interacting with the world."
Larian heard the masses saying that they didn't exactly want to play as someone else's pre-authored character, and weren't enthused for the origin system in a D&D game, and they answered by saying "Here! We heard you! Here's another Origin Character just for you! You can change how this one looks! That's what you wanted, right!?"
With the revelation that you're likely to encounter the Dark Urge later in the game if you don't play as them, this completely cements the fact that it's literally just another Origin Character - with a pre-defined 'default' personality and characterisation. Minor differences in their play conditions, but essentially the same in every way that matters.
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The irony is that it's much closer to what a tied-in custom character could or should be, than the other Origins - closer, but in Larian's usual way, completely overblown beyond the player's ability to make themselves at home in the character... they clearly still do not actually understand what it is about playing your own character that people who desire that actually want.
I'm going to draw a parallel here; The Dark Urge, and the Shard Bearer thence Spirit Eater - there are a lot of surface level similarities here for what these two games seem to be doing, but there are key differences. Mask of the Betrayer does not invade your character to tell you how you feel or what you think; it only describes sensations and urges, and lets the player decide how they feel about them, with dialogue options to support this ability to define yourself... the narration we've seen for Dark Urge often seems to slip into traditional second-person story-teller mode, where it tells you what you're thinking, feeling and wanting; this is the antithesis of playing your own character, and it's something that Larian seem to have never been able to grasp.
The dark theme and overbearing presence of the soul eater was okay for Mask of the Betrayer, because it was built onto the existing backdrop of a wealth of story that you already built for yourself; it was the second game following on from a first; we don't have that here - our only option for a custom character that is tied to the story is this dark and terribly invasive thing, which looks at the moment as though our options are mainly 'revel in being a murder hobo' or 'resist each time and don't engage with any of the personalised content'.
If we had an 'Origin Character' who had some ties to the story that were subtle but essential - something that made the sure connection that we are here, and it must be us, for a present reason, that did not impinge further upon our own character, that would be great - that's more or less what a lot of folks would like; a game that ties our character to the story in an essential way, and gives us elements that can apply only to us, or focuses the call to adventure on us, but which does not try to tell us what we think, or how we feel about any of it - rather that gives us a chance, through dialogue and other interactions, to tell the game how we feel about things and what we think. Dark Urge, if it wasn't such a ridiculous, over-the-top Larian set piece of gore and bloodlust, could certainly have been that... but it seems clear from what we've seen so far that it's not.
