Potty training - poos

Hi all! Little boy has been potty training for the past two days, just pants on through the day. He’s done so well with wees, mostly can tell me before anything comes and only a couple of times has had tiny leak before going to the potty. However, it’s clear today that he needs a poo and he has sat on the potty and tried to do one but no luck. He usually goes every day in his nappy with no issues. I feel like the way he sits on a potty to poo is very different and it might be that that’s making it harder for him. Is it normal for them to take a bit longer to grasp how to poo on potty? I imagine he will end up just going at bed time in his nappy. Thanks for any help/advice!