Generally, kids will learn to stand before walking, but it's no set rule. It doesn't sound like he can't balance when standing, because it takes more ability to balance to walk. It sounds to me that he just doesn't feel safe standing alone. With walking, he knows if he walks across that room there's something on the other side to grab, so it's like a quick fun ride for him to do a quick walk across. But to just stand there with no security, it's not fun and probably a bit nerve wracking for him right now. It'll come in time. Just encourage him to continue walking, walk him him one finger and he'll stop to take a break while holding one finger, and this will be good practice. It'll come when he's ready.
K. B
mom to 5 including triplets