If the exit speed increased, the bat velocity increased. How you are gripping the bat at impact has little to no influence on exit speed.The bat ends up at the pad and fingers. The index finger the hook controls the sweet part of the bat. If you hold a bat and go to impact and stop. Have someone push the sweet part of the bat with one finger. It will give. Slop in your hand between thumb and first finger. Now use this grip perform same test. You wont be able to push bat back.
The ball rockets off the bat with this grip.