Simon has been reluctant to roll-over. It troubled Diana. Dr. Cargo Pants said it didn't matter, particularly given his ability to sit up for long periods of time. Only Simon really knows what's up.
Or does he?
I left him sitting up and went to the kitchen. I could see from the sink that he did a face plant, but there were no screams or protests. I watched him immediately roll himself over. I think he's toying with us.