I don't think this is necessarily an appeal to authority, for two reasons.
First, because some people will treat that authorship credit as a warning label rather than authority; that would make it ad hominem, not appeal to authority.
Second, because it actually gives useful context to some parts of this spec: "Oh, it makes sense that the author of a language without integer types would propose a spec that claims you don't need integer types". That's not a logical fallacy at all; that's perfectly reasonable reasoning.
First, because some people will treat that authorship credit as a warning label rather than authority; that would make it ad hominem, not appeal to authority.
Second, because it actually gives useful context to some parts of this spec: "Oh, it makes sense that the author of a language without integer types would propose a spec that claims you don't need integer types". That's not a logical fallacy at all; that's perfectly reasonable reasoning.