This.
The same ship design is also in Wing Commander - basically, and I could be wrong, I think its to protect the exiting and entering fighters. Upon entry and exit they can not travel at the same speed they might when dog fighting, they have to slow down on entry and begin to speed up on exit. My assumption is this design protects the fighters from being targeted and destroyed giving two large portions of hulls which can put suppression fire on the enemy. Suppression fire is an important aspect of any war mechanics and creates a defensive zone that can be utilized. As I am saying this I wonder if it should be a tube like thing, and the only thing hat negates this and requires a vertical open slot I think would be the veer off. As a pilot in the RCAF basically I know from experience you need to be able to wave pilots off so that they don't crash into downed aircraft on the runway, people, construction equipment left haphazardly in the way, or if the ship hasn't reduced speed making landing achievable. While I am sure its different in space, on Earth landing is controlled crashing. Having both the bottom and top of the ship open for veering off would be an asset. Pilots that come from too steep of a vertical angle can veer down and pilots that come from a low altitude can veer upwards.
Just my opinion.
