The festival have a standard response that any tickets sold like this are illegitimate. Indeed, there's a news article on the front page of the website saying that.
The allowance is 7 shows at 65k each, 2 shows at 50k, and then anything they run beyond that (so the "open house" events and the "all things orchestral" show a couple years ago) is capped at 5k.
Considering how much of a big deal was made of primavera getting Chappell, Sabrina and Charli as their three headliners and seemingly alienating a lot of their regulars….. if Glastonbury manages to get all three plus O Rod and only she is a headliner then woof.
Put me in the camp of only expecting O Rod and Charli, kind of expecting Chappell, and not expecting Sabrina.
Though fitting them all is difficult. Charli headlining other, O Rod headlining pointy, Chappell subbing pointy…. Does Sabrina fill the afternoon a lot on the Other that usually generates massive crowds? (Capaldi, Billie, O Rod, Avril etc.)
Wouldn’t expect Sabrina, but certainly food for thought.