6 month baby not rolling over fully but able to stand and do crunches🤣

My baby is 6 months old now but having difficulty in fully rolling over to his tummy and back. He is always attempting to roll but always unsuccessful, so sometimes we help him with tummy times. Funny thing is, he do crunches like he lifts his head and upper body like he want to stand up, and if we hold his hands, he's like grown man pulling his body up to stand. He also walks and follows us fast in the walker. And we had try letting him stand but leaning on the sofa, and he can do it. It's like hes going to skip the rolling over and crawling milestones and go straight to walking. Now i always see forums and posts that if baby cant roll over by 6 months, he had to be checked up. Sometimes i worry, but whenever i see him do his thing, he seem to be the active and healthy baby. Do we really need to worry? Or is it okay to skip rolling over? Any thoughts or similar issues?