of course rosberg could have stopped once at that point, all he had to do was pit later on his 2nd stop.
rosberg's first softs were a lap younger than lewis's.
He was called in as Vergne was ahead, so was running slower than optimum. Nothing new, teams have switched strategies mid-race all the time, and 38 laps remained. A few too many for either soft or medium tyres. However, why have mediums when you will have to stop twice anyways?