The cmass translation should be included. You can work around this by using @Align_Centers beforehand or use align_epi_anat.py with "-align_centers" or "-ginormous_move". For the align_epi_anat.py options, the center alignment would be combined with the anat-epi alignment at the end with a concatenated transformation. The center alignment in this case would be just centers of the grid. For centers of mass, @Align_Centers -cm or 3dCM can be used too.