Someone on the beta team or Karl, the developer, can address some of the general questions at our new AFS2 RC ATC here.
Here are 24 airports that I used in flight plans to confirm the Spoken Name. There are many others, I just happened not to fly there. Some airports that you might expect to have spoken names, don't and vice versa. It was a popularity contest of sorts way back when this version was being coded. Folks got to submit their choices and someone drew a line. I heard it was 109 for the worldwide list, but, I have not been able to confirm this or find the file that contains the master list.
Naturally, I would expect the really busy airports like San Francisco to be on the list, I just didn't fly there. But, I did find that Salt Lake City, Okla. City, Indianapolis, Las Vegas, San Diego, New Orleans, Kansas City and Houston Hobby are not on the list. hmm.