8 month old isn’t imitating? Is this ok?

I’m not sure what is suppose to be ok or not I’m a first time mom and all this stuff I’m suppose to be watching for confuses me. But I’ve been told that a baby is suppose to imitate you by facial expressions or sounds but he doesn’t do that he will make the sounds later on his own time but won’t imitate you at the time. He laughs and makes eye contact and smiles and all of that but I’m not sure if it’s an issue that he’s not truly imitating me at the time when we are interacting... any input would be helpful. I’m going to bring it up at his 9 month appt.