It can take a long time for his personality to emerge...we've had Ben for 8 years and he still continues to change over the years. His last quirk is head rubs. He loves to have his whole head rubbed. Last year it was butt tickles.
Please note even after settling in more Rocket may not become a cuddler. We have 3 greyhounds now and none of them lay down beside us and cuddle, however, all 3 allow us to come to them and cuddle.
I wanted a greyhound to jog with me...hasn't happened yet and may not ever happen. The point I'm trying to make is that is may or may not happen and you need to decide if you can live with that. We often get so caught up in "expectations" that we miss other things they do that can bring us greyt joy.
Greyhounds are pretty independent and I think many people attach human emotions to aloofness. For example, we adopted a female 3 weeks ago and I can see how folks who do this may consider her "sad". She just follows Ben and Brooke around and really doesn't express a lot of "emotions". Yet, I see it as a greyhound who is fitting in seamlessly, no issues, and is learning to trust us. I know she is attached to us, simply because she now eats when called, loves to go on walks and for car rides, and always greets us at the door.
It takes a lot of courage to admit this, and I applaud you for that. In answer to your question, his behaviour sounds perfectly normal to me. Only you can decide whether or not to keep him in case he never becomes a cuddler. I admit I have never had to deal with this, I accept them as is (which isn't suppose to sound judgemental) so it's not a question I've had to deal with.
My other point is if you tend to attribute human emotions to a dog, you'll likely be wrong and get distressed over it. Has anyone suggested reading books? There's a wealth of information in books such as "The Other End of the Leash" or "How to Speak Dog", books that are geared towards all breeds, not just greyhounds.