Think the best guess is that ORod was originally pencilled in for the Saturday which would line up with her dates either side but they’ve had to move things around, possibly to accommodate the third headliner being a late addition (Neil, or whoever it ends up being).
To be honest, it's a good announcement. When you have 2 of the 3 Primavera Headliners, it can't be that bad. Unfortunately, nothing for me, but that's a matter of personal taste... Can see that this line up attracts people.