I don't think that really makes sense. At all.
The whole point of a later closing time is to give people more hours to see everything on the busy days. Queue times, longer lines for food and slower movement through the park eats up more time, so an extra hour or two or more stops people missing out on stuff. It also spreads the load a bit, as people don't necessarily have to arrive bang on 10am to get a decent amount of time in the park.....
So if you push back opening, you take that away from them...and for what?
The 9pm closing at WnW is perfect in summer, because that place gets rammed. Notice when the park closes at 9pm (4 hours later than normal) they don't push back opening by four hours (to 2pm)...Because that would be dumb.