The phenolic tip does jump a hell of a lot better than a leather tip. My break cue has 2 shafts, 1 with a leather tip (breaks a little better) and 1 with a phenolic tip ferrule combo (jumps a lot better). In the APA, they don't let you use jump cues or switch shafts, so this does come into play every once in a while when you're playing 9-ball or even 8-ball and you have to shoot a jump shot.
There's nothing wrong with jump cues either. It's just a cue that's made for a specific shot, just like in golf where they have a different club for every shot. Golfers never get any sh!t when they use a sand wedge to get out of a sand wedge.
Phenolic GREATLY enhanced jumping performance. I would argue the break isn't any better now because of the phenolic tip, but there is overwhelming evidence that the jump cue has been greatly improved with the phenolic tip. The BCAPL hasn't targeted the jumpers, just the breakers.