The specific language in the rule defines an invalid fair catch signal as "any waving signal" that doesn't meet the requirements of a valid fair catch signal (hand above head, etc.).
The problem with that definition is the word waving. The motions made by Switzer and Reid in no way resembled waving. If the effing rule is that the returner can't make any signal that could be misconstrued as a fair catch signal, then just say that. But don't say it can't be a waving signal, because that's not how the rule is being interpreted. Mark is exactly right that fair catches should be one of the simplest determinations in football.