Bum scooter

So my little one just turned 13 months exactly today! And just officially learned how to sit up on his own from his tummy... lol. Came home from an evening nursing shift to seeing this on the monitor. doctors aren’t concerned but anyways he’s become a fairly efficient bum scooter and can crawl backwards but not forwards. We’ve been trying to show him and help for months but no success 🤷‍♀️ but we’ve been showing him how to sit too and now all of a sudden he’s doing it. Just wondering if once they’re a bum scooter are they always a bum scooter or maybe switch to crawling? Or just skip to walking? Still doesn’t pull to stand yet but can stand for almost 15 min straight if we put him in standing. Any PTs in this group?