Again, even in the scenario you are describing, it is right-to-left when it comes to organizing columns/page layout (just like it would be with manga), but the text is still not right-to-left. It is top-to-bottom text vertical columns going left-to-right horizontally.
There is not a single instance I can think of where the actual text in Japanese would be read/written horizontally right-to-left.
Arguments about modern Japanese text layout is beyond the scope of my original comment, and I don't think it's meaningful to discuss it anyway. Those who know and use Japanese know, and those who don't, don't need to know.
There is not a single instance I can think of where the actual text in Japanese would be read/written horizontally right-to-left.