Just a matter of checking, when did people add Supply Cases to the mix? That information is wrong. You dont get any notification for survivors working on Supply Cases, you only get the notification when they pick up the vaccin. Supply Cases are the same catagory as Jigsaw Boxes and Pools of Corruption. That catagory spawns in the same locations as chests. So just because the Supply Cases spawn in chest locations, doesnt mean they are chests.
I am not logged in right now, so I cannot fix the info right now. If someone else could before I remember I would, that would be great.