I remember how the PL dragged out the Saudis fit and proper persons test. They couldn't really say no, but they knew it was a bad look to allow them in, so just stalled in the hopes the Saudis would get pissed off and walk away - which they would have done if Bozo hadn't intervened.
In Everton's case, it's been 777 stalling, as they couldn't provide the book keeping and assurances the PL requested. But I don't think that was grounds to refuse them. It's the answers a prospective owner provides that allows the PL to say yay or nay; if the buyer is slow to provide the answers I don't think there's a time limit where the PL can pull the plug.
Either way it's more bad press for 777 and more debt for Everton. With a bit of luck they'll be on -15 at the start of next season, with some tougher promoted clubs to deal with.