Open MPI does not release its official tarballs via GitHub; please visit https://www.open-mpi.org/software/ompi/ for official release downloads.
To be clear:
These GitHub "releases" are simply tarballs of the Open MPI git repository at a specific git hash.
These tarballs are not properly bootstrapped, and do not represent official Open MPI releases.
Official Open MPI release downloads are available from https://www.open-mpi.org/software/ompi/.
GitHub unfortunately does not allow us to disable this "releases" functionality, which is why we put this message here (to clarify that these are not official releases).