This is a good general rule of thumb, but not true 100% of the time for all ranged jobs. There are fights where it's better for BLM to be away (though still within aoe healing range, ideally) so that they won't have to move as much, and them being away from the group won't cause any issue for the group. There's also some mechanics where particularly people will want to be away from the group most, if not all, of the time (Ifrit Ex back in 2.x, as a rather old example X3).