...Creating a fancy sort of consistency. Cardassian ships also fire their main guns from the deflector centerpoint of their (this time Sternbach-designed) capital ships. Which shouldn't be a wonder, considering how often our Starfleet heroes utilize the deflector as a weapon!
It does make intuitive sense that this device would be a power or range booster for whatever is fired from its center; perhaps some VFX people even bought into the backstage speculation that death rays don't work at warp, and thought that since the deflector does, the combination would be advantageous.
Sometimes it's a good thing that alien starships have alien features, too; I would have been quite happy with a ship that doesn't fire its beams from obvious beam emitters. Sternbach designed the Cardassian ship with identifiable if alien weapons emitter pyramids, some of which eventually did see use in "Caretaker" and the like. The Romulan vessel never did fire anything from the dome-like features Probert put in for the purpose, now did it?