She skipped a step?

Caitlyn

First off, my baby gets tummy time every day. 10 minutes at least but mostly more. She rolled over ONCE last month from belly to back, but never again since. I thought it was an accident honestly.

Today, though, she's rolled from back to belly about 3 times! Definitely intentional. Soooo...is there any reason why can roll the "harder" way but not the easier one?