Not knowing which faculties at which institutions this derives from (although, one could probably assume that they're not Theist institutions) that is a plausib

Not knowing which faculties at which institutions this derives from (although, one could probably assume that they're not Theist institutions) that is a plausible explanation. However, if you change the Population selection to the "No Affiliation" option the numbers are still pretty skewed in the atheist direction.