There's nothing broken about that. If you want to do full text search, do `man -K` instead of `man -k`. E.g.

    man -K MANOPT

Works for me on Ubuntu 14.04, though slowly so and I still have to ask the pager to search for it within the manpage which is opened. Because of this, I read the manpages when I know where to find what I'm looking for but otherwise just Google.

A far more severe problem IMO is the fact that many Linux distros ship without manpages in their default installs.