I think I know what he means. I so, it's a feature I'd like to see implemented as well (unless it's already there and I missed it).
Basically, imagine you have a large, complicated boss, with many different methods of attacking with it's body.
Say a towering boss monster moved it's hand out to hit you. If the monster is all one big animation, it won't matter if your level with the hand, because the collision occurs at the outer edges of the animation.
Hmm... here's an example.
In the pictures below, the black borders represent where the collision is detected (because it's the outer borders of the animation).
As you can see, in the first picture, you can stand under the attack, and still be hit by it because your within the animations border.
In the second picture, the boss is made up of many smaller animations that are linked to each other to create the same effect. Only this time, the player can stand under the attack without fear.
EDIT: Nevermind. I discovered that GE doesn't have collision on transparency. =P
