The rule could certainly be tightened and more strictly enforced but in my mind (and this is just finger in the air sort of stuff) a lot of stoppages occur because the player with the ball is tackled as soon as they gain possession. And they certainly have no way of letting the ball go. So i feel getting rid of prior opportunity wouldn't exactly lead to that many less stoppages. I'm actually going to make a point of looking for this over the next few rounds to see how many stoppages could actually be avoided by tightening the rule.