In this case, the three people Davis thanked were for checking grammar, a helpful conversation 2 decades ago, and another who read an early draft but had no substantive suggestions. None of these come close to what Carmack was claiming or implying. Davis was simply being nice and thanking people. (I've done much less for people who helped more with some of my publications.)
As I noted before, the reason why Carmack seems to make his claim is tied to his constant need to emphasize his supposed skills and training over others to cover up the fact that he isn't engaging in linguistics but is just acting as a glorified grammar nerd attempting to identify and force EModE syntax and language in the Book of Mormon. If he were actually doing linguistics he would be trying to understand and explain why the supposed EModE appears in the text intermingled with 19th century language, phrases, and ideas. But he can't do that. And so, instead, he throws out ad hominins and dupe people like Ryan by his appeals to his own authority.