Greetings,
AFAIK, it's an undocumented sample class indeed, a rather old example just initialized without having being further developed (so probably quite limited).
Not sure it covers it all and even works
(I had to add a \nofolios after the document declaration, so the page frame might be missing a folio (page numbering) frame - or it's just me -having a modified version of SILE locally with modifications- who broke something, ;)
You might give it a try anyway, and depending on you findings, help resurrect the concept by submitting an issue or a discussion on the GitHub repository?
Regards
Didier.