I can't really speculate on GD mechanics, but a change like this in real life reflects better decision making on the part of the QB. Learning when to take the sack and when to force a throw is a big part of development for a QB. After all, isn't it almost 99% better to take the sack than throw a pick? It does seem, however, that such a big change between years 4 and 5 is a bit much.
It could also be a factor in the teams you played having better front sevens and DBs with frying pans for hands.