“Discourse on the other hand is explicitly conversation focused, and the linearity is a constraint to try to enforce that principle.”
Expanding on this further, this is the structure of a real-world conversation:
Topic A → Question → Answer → New Question branching into Topic B
Tangential idea → Cross-reference Topic C → Further exploration
Contextual loop returning to Topic A
Given the hierarchical nature of linear-discussions, like initial framing becoming rigid constraining subsequent discussions, also causing any disagreement with it to be costly, there is hardly any questioning/refining of the top/parent question/topic iteratively like in real discussions.
Also i think that linear hierarchical top-down structure hinders holistic thinking, it’s reductive in its very essence, posing difficulties in seeing the bigger picture(especially, in subjective domains such as social sciences), unlike non-hierarchical non-linear, a collections of horizantal and vertical cards which enable bottom up thinking, making the contextual coherence of diverse views possible, generating empathy as a result.