Bifolio as a functional unit?

[Aga Tentakulus]

I understand. It doesn't seem to matter for the plants and recipes section. But what about the leaflets? They are significantly larger.
Why are they 2x3 in the astrology section and not 3x2 like the others? Then they would all be the same. How do you explain that in theory?
And what about Q13?
Next question: stacked open or folded.