Ohhh normal je actually! Setiap baby punya timeline sendiri, ada yang early bloomers, ada yang take their time. At 6 bulan, rolling dan meniarap proper itu still very much in the range of normal development, so don't worry sangat.
By 7 bulan onwards, most babies start getting more stable with bergolek, merangkak, or doing that adorable scooting thing, but some kiddos just prefer to chill and observe dulu before they're ready. Someone in my mum group mentioned her son completely skipped the rolling phase and went straight to merangkak at 8 months, gave everyone a fright but he's fine now!
The main thing is: is he hitting other milestones? Can he hold his head steady, track things with his eyes, engage with you? If yes, then he's probably just taking his own sweet time with the tummy time stuff. Tapi if you're genuinely concerned about his overall development or tone, worth checking in with your paediatrician just to put your mind at ease, they can give you a proper assessment.
Aisyah Sphn