With today's environment - reactive covers, slicker oils/conditioners and smoother surfaces - hitting up on the ball creates a rotation that wants to create inconsistency or confusion by how the ball lands.
Creating rotation on the upswing tends to have the bowling ball spinning in the aire...if it lands in the oil/conditioner, it enhances the spin or skid; conversely if the bowling ball lands in the dry/friction, it becomes over reactive or violent...thus you are creating over/under by your release

WRW plays straighter angles and is actually letting the ball on the downswing and Ryan spins it more than the average pro
So out of all that...to disagree with my analysis you pick 2 out of a 1000...

It's about how the ball bleeds off energy...one that bleeds slower tend to be more controllable and one that bleeds quicker becomes more inconsistent

Ok I'll give ya that
If you look at WRWs years ago, he did hit up more on the balls say in the 90's compared to the 2000's...it was on the bottom of the swing but it does still appear as if he hits up
Ryan has a similarily different motion...even tho he hits up on it, it's at a more downward motion into the lane...he has a more upright swing...and Ryan comes more from the inside of the ball

It's like watching something in regular speed vs slow motion...slo mo it and you see the subtleties...they adapted over the years very similar to PDW....

^^^^ I think it's dependant on the bowler/generation... Older bowlers may be on the category of hit/lifting up, while younger modern folks the opposite. Im pretty sure there are many old school dudes trying to learn the modern release like myself....some have adapted to the change very well.

Correct. When I started bowling 50 years ago, we were taught to "hit up" on the ball. We were also taught to keep our spine angles more upright than what you commonly see today. We were also more on the side of the ball, especially at release. By keeping a more upright (spine) angle, we were better able to impart side rotation on the ball. It also tended to keep axis tilt from getting too extreme. If you haven't changed your game from this style, it is still the most effective position in which  to release the ball, contrary to what some well intentioned instructors are teaching now. If you are trying to develop the dynamics of the modern (power) release, then more spine tilts (both forward and lateral) are essential.

However, regardless of whether you are an "old school" or contemporary player, both styles will do much better by NOT hitting up on the ball, as JustRico pointed out. I am still old school, but I have a much better release when I concentrate on creating a "flat spot" with my follow-through. Since I am more erect and I am more on the side of the ball, I have to concentrate on using my knees more at release rather than more spine tilt.  By releasing the ball lower and flatter to the lane surface,
 the ball's energy is not diminished but instead, it is preserved where it is most needed--at the breakpoint.