I don't know what is up with Quinto but it seems like he is not just happy.Unlike Chris Pine, Quinto hardly talks about the film.
Maybe Quinto just isn't as skilled at talking for a half hour and saying nothing as Pine is or maybe he's busy with American Horror Story and not available
Remember, they're all under orders NOT to talk about the film too much. Maybe Quinto just thinks it's easier not to talk about the movie at all rather than watch his words all the time.
When I working on the DARK KNIGHT RISES novelization, I adopted a policy of total radio silence regarding the movie, even with friends and family. It was simply less stressful than constantly parsing my words and wondering what I was allowed to say about the movie. Didn't mean that I hated working on the book or thought it sucked or anything like that. I just decided early on that I wasn't going to talk about it, period, so I wouldn't accidentally slip up and reveal something I wasn't supposed to . . . .
Plus, some actors (and authors) just like talking about their work more than others. There are actors who love
promoting their movies and dealing with the press, while there are other actors who would rather have a root canal. Doesn't mean the latter hate their films or have something to hide. They're just not into the dog-and-pony show aspect of the business. They're about the work, not the publicity.