Unless, I am misunderstanding something, it seems like several of the documented keys for \hologoFontSetup are not actually defined. For example, bibsf. The following example errors with Undefined key:
\documentclass{article}
\usepackage{hologo}
\hologoLogoSetup{BibTeX}{variant=sf}
\hologoFontSetup{bibsf=\sffamily}
\begin{document}
\hologo{BibTeX}
\end{document}
(Unrelated, but even without \hologoFontSetup I see no difference between the normal and sf variant.)
The other documented but undefined keys are rm, sc, sy, and logo. This applies to \hologoLogoFontSetup as well.