Well, this is a super old post but as a mom of a child with sensory integration disorder----------- these were symptoms of it. It absolutely sounded like sensory and I hope that they sought help with an occupational therapist.
he might have SI or some type of asperger. I baby sit a girl who is diagnose with SI and has the same symptoms. The best book to read to understand your child is The Out-of-Sync Child: Recognizing and Coping with Sensory Processing Disorder. You need to start working with your child as soon as possible before they get used it, they need to learn to be normal.
i agree with jdtm. it does not sound like a sensory integration problem. i think you are describing echolalia, which can also be a symptom of other problems. sounds mostly like delayed echolalia. you can look it up, and definitely bring it up to your child's pediatrician. he can refer you for evaluations and therapy. if you are in the states, your school district's early intervention can help as well. best of luck.
From your description, it does not appear to be sensory integration disorder. Sounds more like a child who has not had a lot of opportunity interacting with other children and one is quite cautious and timid in physical activities. We have one grandchild this way, but he is very introspective and a deep thinker. No one person excels in all aspects of human nature; and no one aspect is better than another. Any other thoughts ...