Everton haven't stated that.
They're said public safety is uppermost and there should be full disclosure of the information - which is a legitimate request considering we were 4 hours away from a Premier League match with fans in attendance.
There isn't an issue with Man City here. The issue is with the Premier League.
Everton statement:
Everton Football Club regret the postponement of tonight’s match against Manchester City - not only for the 2,000 fans who would have been attending, but for supporters on Merseyside and across the world.
Our players were prepared for the game, as were both the team staff and everyone at Goodison. Matchday is the most important date in our calendar. And this was a big one.
Whilst Everton will always have public safety uppermost, we will be requesting full disclosure of all the information that Manchester City provided to the Premier League so the Club can be clear on why this decision was taken.