Possible error in the differences between vertical writing mode and horizontal writing mode

[xfq]

In item a of § 2.3.2 Major Differences between Vertical Writing Mode and Horizontal Writing Mode:

Vertical writing mode.

[...]

Columns are arranged from top to bottom. A book starts with the left (recto) side and progresses from right to left (see Figure 21).

[...]

Horizontal composition.

[...]

Columns are arranged from left to right. A book starts with the right (recto) side and progresses from left to right (see Figure 23).

If I understand correctly (although I'm not sure), these two points mean that in the vertical writing mode, the reader opens the book from left-hand side to right-hand side, because the block direction is from right to left, so the book cover in on the left. If so, "opens from" might be better wording than "starts with". I'm open to better suggestions, of course.

Also, "recto" is used in both the vertical and the horizontal case. Should one of them should be verso? Or because recto in horizontal and vertical writing modes are different sides, both of them should be recto?

[himorin]

Please check figure 21 and 23.
Usually, back side of front cover (verso in reading order) is kept blank in (traditional? thick?) Japanese book.

[xfq]

I have looked at these two illustrations carefully. So IIUC "starts with the left (recto) side" doesn't count the blank page?

[himorin]

Yes, usually (in Japanese book) cover 2/3 are not included in the main body or not numbered, that's why page 1 starts from the main body (but not cover 2/3) in fig. 21 and 23.