Whatever was behind this particular case but normally airline procedures (approved by Authority) stipulate how many pax of each "type" (other than "normal" pax) could be onboard of particular aircraft type. At our outfit we have a certain limitation on number of pax with disabilities, number of unaccompanied minors, number of police-escorted criminals etc. This is all about emergency evacuation.
I remember the case when we have been doing a charter to carry 40 blind people to some kind of conference for blind people and in order to carry them we have applied for one-off exemption to Authorities and got a written consent from our insurance company.