New to DD, what exactly causes the dreaded Good/Okay?

[Jbob811]

In real baseball, which this game is supposed to simulate, if a player, lets say Mookie Betts, gets good timing on a fastball that is straight down the pipe at 98 mph, then it will be a rocket off the bat of over 100 mph. Granted those rockets may not always result in a hit, but they are rockets nonetheless. Why is it in this game in the exact same scenario I hit a lazy fly ball to the outfield at 85 mph exit velocity?

[bhall09_PSN]

Curious for everyone, what percentage of your perfect-perfects are on pitches right in the middle of the zone. I've gotten a few on pitches near the edge of the zone, but a large percentage of mine have been simply just pitches in the middle or close to the middle.