Originally posted by overlord
eer
Ditto.
It's actually made clearer in the novelization. The only reason Obi-Wan was able to beat Grievous was because he was using soresu. He was able to block Grievous' stikes to begin with, but Grievous kept speeding up his attack rate. That eventually overpowered Obi-Wan's ability to block, so he let the strike through, but severed the lightsaber's emitter a split second before it would have decapitated him. He did this a second time, so Grievous only had two lightsabers, which made him much less of a threat. However... He then used a Force Push to get Grievous away from him, he didn't actually beat him by duelling. If Obi-Wan had used ataru, Grievous would have been able to track his movements and slash him in mid-air, just as Obi-Wan was able to do to Anakin. I suspect that had Obi-Wan not used a Force Push, he would have continued to sever all Grievous' sabers and then decapitated him when he was unarmed.