You might say that this is a transitional scene. In TAS we see these as phaser banks, so having one as a phaser bank with The Cage type cannon before one, and a new tube in the other.
I might say the lower sensor dome was more, that it emitted phasers and blob type torpedoes as well. As dilithium became more scarce, we saw move to blister phasers, which you might have on the top of the saucer, but not the bottom.
This way you have a little of everything.