Worried about 9mo baby?

a relative of mine has a 9month baby and im concerned about his health/progress.. he spends all day in his bouncer, he cannot sit unsupported, shuffle, crawl, walk, talk/ babble or do anything other than sit back (supported) and watch the world go by. he is responsive, eg; he laughs when played with and makes eye contact etc but im worried he is not getting the input he needs to grow properly, he is also still on formula not solids. im currently pregnant with my first so dont know much about babies progress, but is this normal?