After spending some time looking at the code, its history, and the corresponding doc, my conclusion is that `bind-map`s code was probably incorrect already with older Emacsen (just in different ways) and its intended behavior is far from clear, so I think it's best to leave this as a WONTFIX and let `bind-map`s authors figure out what to do on their side (tho I'd be happy to help them figure that out).
You don't think we should even restore it and mark it as obsolete?
Since I believe bind-map's code was only half-working to begin with: no, I don't think it's worth the trouble. It would just help them muddle through. I'd rather help them fix their code for good.
Stefan