Makes one wonder if the Kirk-era Enterprises had catwalks in the nacelles.
In TAS "One of Our Planets is Missing", Kirk and Spock take a bit of antimatter into what they call "the antimatter nacelle", using a catwalk in the center of a horizontal cylindrar volume. It wouldn't be that much of a stretch to claim that this is one of the warp nacelles, perhaps its very bow - and indeed Doug Drexler created his TOS ship cutaway drawing with this theory in mind, and it became sort of canonical when used in ENT "In a Mirror, Darkly"...
Whether we are to literally believe that one nacelle is matter, the other antimatter... I'd prefer not to. Jump-starting the drive from just one nacelle, rather than from Main Engineering, must be a special backup-of-backup scenario that might have its special procedures; perhaps only the starboard one is configured to receive the jumpstart dose of antimatter, and therefore enjoys this odd designation?