Baby 4 months and 1 week old. Can roll over, grasp toys, cheerful, gur…

Baby 4 months and 1 week old. Can roll over, grasp toys, cheerful, gurgles, lies on tummy well and for a long time, pulls up knees like he wants to crawl, in general everything is according to age. But in the back position doesn't lift his head during traction with hands, doesn't strain the handles, just lies and laughs?. I have an appointment with a neurologist, waiting for it. Question, who had the same way? When did they start pulling up? What did the doctors say?