Plate Coverage - If your hitter is doing this drill properly they will find that they are able to drive different parts of the zone much better. This is because they are now in a better hitting position which will allow for more adjustability throughout the swing. Being able to crush the ball in your sweet spot is one thing, but being able to make solid contact on pitches low and away or up and in is what makes you a real hitter.
Direction - Since the hitter is now able to get their hips back and in a hinged position there, being able to stay through the ball will be much better. Hitters with tall posture have a tendency to pull and spin off the ball. With the chest over it allows for the bat path to stay in line with the pitcher, making the hitter have a better chance of crushing the ball.
Hard Hit Balls - getting in this hip hinged position truly sets the hitter up to crush the ball. Without this posture, the hitter is not loaded properly and won't get the most out of their swing. The lower half is now fully loaded from this position and when a hitter decides to swing they will hit the ball much harder than before.