Okay, here's the interview:
An Interview with Adam Elliot
Apparently the
real correspondence was initiated by the person with Asperger's Syndrome, who hand-writes the letters because it feels more personal. This is not the behavior of a person who is antisocial and emotionally crippled. Elliot says that though his friend knows about the movie, "he hasn’t been overtly enthusiastic, which is kind of what having Asperger’s is all about." But obviously that's untrue, because the very next thing Elliot says is "At the moment, he’s going through a phase where he’s interested in what’s going on, googling all the interviews that are coming out." This is not the behavior of an uninterested person. This is just a hunch, but maybe the guy understood from the script that he was misrepresented, and acted "unenthusiastic" rather than "annoyed" in order to be polite.