I think that the important point in the preamble is that the third hint gives the total number of five-letter words that
must appear in the completed grids. This suggests to me that there should be at least the number of words given by the hint, not that there should be exactly that number. So if we can find additional words by reading backwards, that doesn't create an inconsistency.
This was certainly a challenging puzzle. I think that the setter should be congratulated for building in an alternative, but ultimately incorrect, pathway that provided a sequence of letters that, when put in ascending order of the numbers they represented, included a number that was plausible for the number of words in the grids, albeit incorrect. I benefited greatly from the hint about 2dn given in an early post, as I'd gone astray first time round and found that I couldn't reconcile the elements in 7ac because of an incorrect value for t.