It’s been part of the theory since the very beginning - it’s why you find it under Plot Dynamics, not Character Dynamics. It’s why it is called Story Judgment and not Main Character Judgment.
The theory book is not perfect in its description of every single story point. Occasionally they took shortcuts in an effort to help explain certain story points. The shortcut for this is whether or not the MC resolves their personal problems as that is the closest connection an Author has emotionally with the Audience.
I found this for you, which might help:
- Chris Huntley on the Story Judgment a post here on Discuss Dramatica. It looks like he accidentally labeled his description of Story Judgment with Success/Failure, but you should be able to see what he was trying to say.
Many of the podcasts over the past twenty years deal with this story point, though I can’t remember exactly which ones. Might be time to get somebody to transcribe them all (not me).