Are Foldouts Always Shorter to Left but Longer to Right?

[ReneZ]

If I’m not mistaking anything, it seems that the only evidence is the mis-placed gathering mark.

Indeed and I had almost forgotten about that point.
Whoever wrote he gathering marks clearly intended the binding to be in the place that is now the fold
in the middle of folio 67.

This writing of the gathering marks must have taken place before the binding and was probably the first preparatory step for this binding. The very presence of gathering marks means that the sheets were intended to be bound into a codex, stacked into quires (one way or another).

There are still unanswered questions. The early mix-up between herbal A and herbal B folios happened before the gathering marks were added. This is because, for example, the 5th quire mark is on a B folio.
There are several different possible explanations for this.