I posted yesterday (I think it was yesterday ) in Cute & Funny about how Molly is starting to get silly and playful after a little over two years in my house. She would have occasional bursts of playfulness, but most of the time she was rather reserved. She rarely comes to me for affection, but is happy to get it if I go to her. Yes, she is a Princess . I never really got the sense that she was unhappy or uncomfortable here, I just thought (and still do) that her personality was more reserved and quiet than outgoing and playful. My first greyhound was like that, but she was very shy and timid, which Molly is not. I am kind of a quiet, stay in the background kind of person myself, so I guess it didn't bother me that she was also like that.
Also, I have two other greys that are the opposite. Fletcher is a mama's boy who is always in whatever room I'm in, very playful, a real goof. Sallie, my newest girl, I call an affection slut She will go up to anyone and put her head in their lap, and stay there as long as they keep petting her. She thinks everyone who comes to the house has come to see her
I guess my point is, three months isn't very long, and he will probably continue to come out over time. That being said, his personality may just be somewhat reserved, you can see from my examples above, greyhounds come in all "flavors".