I looked briefly at the site and I see the author mentioned use of stick or post & beam framing. Because compression of the bales will occur over time I would use as much framing as possible to endure structural stability. The weight of the roof combined with the weight of the upper bale walls will crush the bottom of the walls. Every year there will be more and more compression.
I would stud floor to ceiling around my doors, windows and corners, plus add intermediate wall studs. The framing will make it easier to secure exterior sheathing and interior finishes as well as support the roof.