I would imagine (on the Enterprise-D) that it's not right next to the bridge, but below, and that one set of doors on the bridge can take you to there, whereas the other way to get through to the conference lounge is somewhere below the bridge, on deck 2, where I believe the lounge is located. If I interpret "forward observation lounge" correctly, on the Titan (and other Luna-class Starships), it could be facing forward and still be on deck 2, and you might not be able to just simply take entrance #1 on the bridge like you would in the Enterprise-D.
I guess I need to grab the book, although I'm yearning for older ones as I'm less-hesitant to grab 'em first. I guess it's just the way Berman recently took Trek in both the Pre-TOS and late-late-TNG-eras. However, I do like the description of the Titan in its words, so I might go ahead and find out stuff on it by getting the books...