I have also noticed this issue with openmpi's mpirun. Surprisingly it breaks some 3rd party scripts that try to guess the mpi system from "mpirun --help". Whether they should or not is a different question.
I asked apt-file, and it told me e.g. help-schizo-ompi.txt (nice name btw) is in libprrte-dev: /usr/share/doc/libprrte-dev/help-schizo-ompi.txt This package is installed, but I suppose mpirun is confused by the /usr/share/doc location.
