[SPOILERS of course, and unnecessary word-of-god-ing]
Symbolically, I didn't mind breaking the rule because to me the game was never about "real words" (a rather arbitrary category), but rather the sets of 12. NOWEV.....YSA fits the theme of puzzle 12, and so IMO its valid. (After all, f8 f9 of puzzle 8 is effectively gibberish, so why not have actual gibberish?)
...but that's basically a post-hoc excuse. The real reason I changed is that the shorter message was often confusing to players, and seemed a bit anticlimactic, and I couldn't come up with a suitable long semi-palindrome.