The hlsdemux HTML doc is installed, but no HLS demuxer, although to my understanding it should be installed.
I suppose this is gst-plugins-hls, so the bug is kind of void unless you consider the fact that the documentation is being installed by ...-bad. I'll just make some use of this bug and change the description accordingly, though I don't think the problem warrants a bug, therefore I have no opinion if it's being closed.
Yeah, it'd be too hard to split the docs too, so those are shipped in the main package still. Maybe something will be possible to look at as we move to meson, but I doubt it.