2.2.3 [W3C-EPUB3] Section 3.4.12. The spine Element
C0006: There are no mechanisms to override the default direction
The specification states:
› 3.4.12 The spine Element The spine element defines the default reading order of the given Rendition of the EPUB Publication content by defining an ordered list of manifest item references. ... ... Reading Systems may also provide mechanisms to override the default direction (e.g., buttons or settings that allow the application of alternate style sheets).
There are no mechanisms to override the default direction.