Nature of EX-Gym distribution
Are there any solid data on how exactly the EX-raid invites have been distributed? In particular, did Niantic sent out the normal amount of invites to independently random gyms? In which case chances are high that at each gym only one player will have been invited. Or did they sent blocks of invites to random gyms? Somebody more involved in the game probably already knows whether their S2 cell has much more different gyms this time around.
Answers
^this
People were getting too close to working out EX raids. There was at least enough understanding to start triggering raids more frequently in many places.
Niantic like to keep things ambigious, for what ever reason.
They seem averse to accurate and detailed information
It could just be that they heard people saying it wasn't perfect, and so they have continue to improve the system - clearly more people have been invited recently than were previously. So if we give them the benefit of the doubt, it could be viewed this way.