It can actually be debated whether those four plus four windows are for the Rec Deck. That is, they cannot be for the Rec Deck - it's physically impossible. If the facility is as high as shown, especially in relation to the height of the windows, it simply won't fit on the saucer rim.
It could then be argued that the Rec Deck is somewhere close to the core of the saucer, without windows, and the interior squares showing an outside view are actually just viewscreens. Which frees all the rim windows for other uses.
Andrew Probert has been a proponent of the idea that the Enterprises should have small, intimate contemplative spaces with a view to space on the saucer rim. IIRC, the TMP novelization mentions that concept, too - something of a counterpart to holosuites when it comes to keeping the personnel happy and sane. The rim windows could be for such rooms, or then for all sorts of more officious lounges and meeting rooms, or VIP quarters.
OTOH, the Avenger Class Blueprints by Mike Rupprecht and Alex Rosenzweig display a layout where the windows simply open to a rim corridor. Generally speaking, the outer rim of the saucer would have to be considered an "extension" of the original structure, accounting for the greater diameter of the TMP saucer vs. the TOS one; one then wonders why the extension was made, that is, what crucially important spaces were added.
Timo Saloniemi