For the same reason, the boards are rotated 90° in the Z-axis when viewed from above.
When viewed from the front, a weaving board, including the four warp threads, is now only about 5mm thick.
All ten cards lined up next to each other are therefore about 5cm wide.

The process of threading the warp threads into the small boards is called warping.
A warp thread passed from the back left - through the hole - to the front right is called S-warping.
A warp threaded from the other side of the board is called Z-warping.
That is:

Turning by 90° results in two further factors to be considered:
Let's look at it from above:
The clockwise rotating board, now rotated 90° counterclockwise in the z-axis, rotates forward from our point of view.[Picture top left]
Looking from above, the four warp threads each pass through a hole (not shown in the picture) from the back left to the front right, a so-called S warp. This still gives the same S-twist in the twisted yarn.
The clockwise rotating board, but now rotated 90° clockwise in the Z-axis, consequently rotates backwards.
But it still results in the S-twist on the twisted yarn.

A board covered in Z-warping turned to the front therefore results in an S-winding of the twine.

A board covered in S-warping turned to the front therefore results in a Z-winding of the twine.

So a board covered in Z-warping turned backwards results in a Z-winding of the twine.

A board covered in S-warp is therefore turned to the back and results in an S-winding of the twine.

The board warping thus results in a very specific pattern in the ribbon.
Thread colour, direction of twist and warping thus cause the many colourful, pretty patterns of the ribbons. For thousands of years in our global cultural history.

Direction of rotation and windings