The muse package installs the info file into /usr/share/info but
no 'dir' entry is installed.  This means that muse is not shown
in the top-level info page.

You can see this by starting emacs, typing C-h i, then searching
for 'muse'.

I think the problem is probably the %post script:

/sbin/install-info %{_infodir}/muse.info %{_infodir}/dir 2>/dev/null || :

... the file is called "muse", not "muse.info".  And as it is gzipped
perhaps it should be referred to as "muse.gz" here.

This also affects the %preun script.

I haven't tested my theory, so take with a grain of salt :)