It's just strong rumours based on people who have provided good info in previous years. Can't really call it evidence I guess.
To an average joe the 1975 seem unlikely cause they haven't got any tour dates yet.
It's certainly been done a few times before, although with an afternoon Pyramid slot, 2007 The Waterboys headlined Avalon Friday, Acoustic Saturday, then played an early afternoon slot on the Pyramid on the Sunday. I don't recall the circumstances behind it, whether one of the headliners was as a fill-in for someone who pulled out, or whether it was something they asked for?
2008 Seasick Steve headlined the Acoustic and then played afternoon Pyramid.
There'll be a fair few others I'm sure.
Worst thing I鈥檝e heard is if you鈥檙e semi decent at the work you get shifted into busier bars as a reward, whilst the useless people get the rest of their shift off, not sure how much that reflects the wider experience or if it鈥檚 just my grumpy mate