The main thing for me was that Veltman was considered to be about to take the free-kick (I use the word 'considered' carefully!). Whereas no Arsenal player was about to take the throw in - so Pedro wasn't delaying anything. I guess context is also relevant. There was no reason for Pedro to be wasting time, and indeed he wasn't - it was more to do with frustration. Whereas Rice was on the side leading 1-0, and had every reason to waste time.The main thing is, if its off the pitch, there is another one nearby that can be grabbed, if its the ball on the pitch, that is the one you have to use.