I really don't understand how this comparison works, because when I throw an underhanded spiral it seems to roll off the palm side of my middle and ring fingers, but I don't see how that relates to the bowling release because it seems that my release is going straight through the ball in a forward direction, with no contact with the palm side of my middle and ring finger. Can anyone explain this motion?

What you are describing is coming straight up behind the ball. Which is one way to do it. It creates an earlier roll. But if you want to create a bit more length and a stronger breakpoint move, then you need to rotate more off the side of the ball from that "behind the ball" starting position.

Erin

And, keeping the weight in the palm of your hand (the sensation you are describing with the football) will give your fingers more time in the ball before gravity pulls it off. This will give you maximum revolutions and will keep your hand in a strong position as long as possible. Next time you are on the lanes, just imagine that bowling ball is a football and try it, it sounds strange but the comparison does work.