Also, in Phase II those aren't torpedo tubes, that was the phaser assembly. That feature was modified into the torpedo tubes for TMP.
In Phase II phasers acted like both beams and energy packets (like in Balance of Terror
). The feature was added to give a physical location on the miniature for the effects people to work with as this was an issue during TOS (where the Enterprise miniature had no physical weapons visible). One of the biggest shortcomings I've seen with people attempting to complete
the Phase II design is attempts to add features that Taylor and Probert came up with for TMP.