U need to see developmental pediatrician physical consultation to check with his behaviors

Hi Sorry to hear your son's issue: If I can restate your query, it is that "he doesn't initiate conversation despite having necessary vocabulary", right? Nowadays, there is an increasingly common trend of social and  communication&language delay, unkindly labelled as autistic trait...for this, you need a proper developmental assessment (by any kind psychologist) along with baseline screening of hearing, vision, etc followed by a visit to a higher center with developmental pediatric setup.