In the first still of the Enteprise in the OP, the dish is inoperative (gold). We've also seen other stills of a heavily damaged Enterpise with a non-working dish that is very damaged (a piece is missing).
The ship that crashes into Alcatraz has a working (blue) dish that looks to be undamaged (fully round -- a large chunk of the Enterprise's was missing).
makes a good point. It's hard to believe that ship wouldn't go cartwheeling when its saucer hit the water at the angle it did. The only thing I can think of is the distance from Alcatraz to SF is not very far, and it hit land before it had a chance to cartwheel (because for a split second, it does look like it could flip over).