[baxtr]

Would have been great if they organized this document exactly as they propose. But they don’t? Which is a bit weird to be honest.

[taneliv]

But they sort-of do, no? The left hand side bar has the top-level (bold) headers "Home", "Start Here", "Applying Diátaxis", "Understanding Diátaxis" and "Colophon". The middle ones could well be labeled "Tutorial", "Explanation" and "Reference", but that would be very confusing for the reader!