There’s a number of snippets where it’s clear where the author is going:
Johnny and Maria both strongly deny the presence of chocolate or cocoa in their recipe but do attest to about eighteen different spices in their blend.
Many years ago, a food writer thought that he tasted chocolate and maybe even licorice in Cincinnati chili. In January 1981, the Cincinnati Enquirer posted a recipe for Cincinnati chili that included half an ounce of bitter chocolate
It is possible that the sweetness some have associated with chocolate may be attributed to sherry or sherry vinegar.
One legacy chili parlor owner things that Skyline uses sherry vinegar to impart the sweetness that people like and that some mistake for cocoa or chocolate.
It’s not definitive, but I remember reading a less-excerpted segment version of this book where it was clear the author believed chocolate was not typically used by the chili parlors. Johnny and Maria from my first quote are of Camp Washington Chili (a Cincinnati chili parlor of 75+ years.) This is also not to say that maybe some joints do use it, or that maybe that Enquirer article has inspired people to use it, but it seems at least plausible, if not likely, that the original chili parlors did not use it. The quote about the possible licorice taste, of course, would put fennel as a prime suspect for that flavor, or possible aniseed or star anise. I do not recall tasting anything like that in Skyline chili, at least. Don’t know about the other parlors. With an 18-spice blend at Camp Washington, it wouldn’t surprise me if fennel is one of them. It makes sense to me. Oh, I suppose tarragon could be another possibility, but it just doesn’t feel right to me.