Or, like the additional work-stations on the bridge of the D in Generations, are we meant to assume that in-universe, it was a structural addition made during some refit between the original series and TAS?
That seems rather likely.
The original configuration might have been: Single turbolift. First stop is the 'outer ring' corridor FJ spoke of, then it continues down into the ship. The refit probably added the second door for direct access to the outer ring corridor.
(Or perhaps the second door goes to a briefing room, like Voyager