Joe might be seeing fansites spreading their own rumors. If Supergirl is disconnected to Superman, that makes no sense. It's not like Gotham with no Batman, Supergirl shares her villains with Superman. As for CW rejecting it, I call bullcrap since CW days ago said they were planning to add more DC shows to their schedule.
Well the CW passing on the show we've known about from when the show was originally being shopped around.