Mama's intuition is a powerful thing, so if you are worried, take her to your ped or get an EI just in case.
That being said, my DS had very little interest in movement until 10.5 months. He was just a very content, placid little guy, always hated tummy time and didn't roll over much either. And was never particularly interested in things he couldn't reach. Then one day he just started crawling. He walked at a normal age and ever since then has actually been physically advanced for his age.
Crawling isn't actually a milestone so I'd be surprised if anything is wrong but it sounds as though the PTs and other medical folk think the not-putting-pressure-on thing sets off alarm bells. So talk to your doc and take it from there!
Laurel
Mama to Jack 6/02 and Maddy 12/04
Babywearing education in Napa, CA