Valla was pretty average with all milestones up until she began walking I would say. Initially, I remember her army crawling and then regular crawling, then she went straight to walking unassisted at 12.5 months. She never cruised furniture.
9 months seems okay still, does your child try to get around in a different way or show progression physically? I know it can be worrisome, but if crawling isn't actually a milestone I wouldn't worry. We have a family with a daughter 14mo older than our daughter, and she still preferred to cruise furniture at about 15-16 months. Now she is totally typical physically. They really are so different. I think too, that if one area is advanced, it's not too surprising another area is lacking--I think it's quite common.