This is an interesting idea and I think you're absolutely correct about childhood make-believe being a kind of patient zero for the behavior, but my impression of Nordic is that it's more focused on achieving the psychological bleed and then breaking it down afterward
As a lifelong GM I'm more interested in classifying the cultures by what they do whether than what they intend to create. That is to say, "What is the process of play?" If we described exactly what the group was doing and how they reached decisions, that to me would be far more descriptive than saying why they were doing it.
Intention in my experience is a very weak classifier, because a lot of people intend to do one thing and end up doing something else. I'm much more interested in what you are objectively doing, and I'm telling you that your described processes of play looked very much like processes of play I saw in the LARP community in 1992 to 1996 and especially in the online "LARP"/cyber community with its text based play. The essay talks about the first appearance of Nordic as a culture in essays written in 2000, but I can attest that up to a decade earlier than that, online LARPing communities were achieving (if not as a stated goal of play an actual consequence of play) so much bleed that it was at times a serious and real psychological hazard.
One of the hallmarks of that style of play was players who spent more time IC than OOC, that is to say, they were IC for 12 or more hours per day, until they began to self-identify by their character name and not their "real" name. Another hallmark of that era was there being little or no real distinction between roleplayed romances and in real life feelings. That is to say, the role-played crush was also often that person's first real life crush. Role-played romances were often equivalent to long distance romances. Is that enough "Bleed" for you? But again, to me that the process could create "Bleed" and that bleed is addictive especially to personalities with low self-esteem, and that at some point someone could identify "Bleed" as the goal of play, doesn't change the concrete process of play that was being performed whether or not it was being performed to achieve bleed and whether or not some players were experiencing or intending to experience bleed and others were not.
To me the definitive proof might be something at the age you were involved you couldn't answer, but the definitive proof to me would be whether ERP ("TinyS*") was going on through private communication channels.
When you write a description of "Neo-Trad" play as:
"and is more centered on the ability for the participants to step into a thematic context and live out the identity of the character"
Then that's immersive play and whether or not Bleed is achieved isn't really to me the point. You're going to get Bleed from at least some of the participants in any immersive play, whether or not that's the goal of the whole group and whether or not anyone is trying to do that. The point is a concrete description of how you go about "stepping into the thematic context and living out the identity of the character".
For me I can identify what the essayist calls "Nordic LARP" by whether or not method acting techniques and self-identity as the character is occurring consciously or consciously as an aspect of "playing the character" and whether or not that thespianism is primary to play, and resolution of conflicts mechanically is secondary to that or even ignored in favor of allowing the participants to reach their own climax of feelings so that they feel the conflict is emotionally resolved. And that to me is something I've had described to me from middle school make believe play going back into the 1950s, where nobody had really figured out how to turn make believe into an RPG yet but they were still identifying with the character both in and out of the game and the lines between character and actor were blurred. And it differs IMO from FORGE Story Games because no one is using Fortune at the Beginning or Narrative Currency to tell you what you ought to feel or do with the scene. In other words, there isn't a narrative director assigning roles to the scene so that you are playing something more like traditional Theater Games with a way to manage role assignment.
I guess my larger point is that as someone who has been in the community more than 20 years longer than you have, the "Cultures" essay while interesting and having some kernels of truth in it, vastly understates the real complexity of the real RPing community.