I'm coming late to the discussion but just to add my two cents, I think the divider makes sense. I have a small 15-pound dog who has been bitten twice by dogs three times her size. Both times the dogs got away from their owners and both times I really feared for my dog's life. And here's the funny part, both times the horrified owners declared they had no idea their dogs were capable of that.

If you have a bigger dog, I'm sure it doesn't matter whether there is a divider or not. But if you have a small dog, yes, it makes sense.