"This is one of those items which belies the supposed infallibility of TMoST. The book came out between seasons 2 and 3. The "recreation area" is, I am given to understand, the first inclination to what would be become the holodeck on TNG. It also made an appearance on TAS ("Practical Joker," IIRC). The line about the set having already been built and the promise that it would be seen in season 3 is patently false."
No, it is not. TMoST refers to "4 major facilities" on the Rec deck:
1. large recreation area
2. main food preparation area
3. ship's laundry
4. exotic entertainment center (presumed to be holodeck)
Original quote: "Although this recreation area has never been shown in any past episodes, this set has now been built and will be seen in the third season."
In Season Three we saw the Herbarium as part of the recreation area (soundstage 8) for the first time, so the promise was kept.
I assume that the "Life Sciences Botanical Section" from "The Man Trap", where Sulu is enjoying his meal, connects somehow to the Herbarium.