I think I finally get it. The reason it didn't click for me is that thus far, terms on the right column seemed to follow a rule that they always had to form a valid word or phrase when read from right to left. "nowevahwonuoysa" would be the only one not to follow that rule. Actually, more than that, it breaks the bigger, more important rule of these "word searches" always involving searches of actual words, not simply nonsensical letters, so long as you see right-column terms as simply being reversed.
I didn't notice that the puzzle 12 hints were all the same as the bottom-right corner hints, even for ones that go in the right column, which would indeed necessitate writing them backwards. I think I would in fact find it more intuitive if you instead switched up the puzzle 12 hints for the right-column terms as you say ("n8" for "notraceof"), so that they would get written the same as on the previous pages, and this would allow the final term to also follow the pattern of being valid when read backwards from how it's written. Then you could do one last page after where everything gets written out properly, with the right-column terms only reversed there for the final message.
I can see what you were going for, with the elegance of having the final puzzle also serve as the final message all at once, and maybe this isn't an issue most people would be confused by like I was. But speaking for myself at least, it almost made me miss the final message entirely, and I think my suggested approach would help ensure that people understand exactly what you want them to see at the end.