"Your just looking to argue, but you know you are wrong." Think you might need to look long and hard into a mirror for this one, friend. I am not being argumentative at all, simply honest. I also don't think I am wrong at all. In fact, I 100% believe that you and the other poster are wrong here.
The initial point of discussion was why get a JB cue at all instead of a break cue and a jump cue. I provided an explanation. Fact of the matter is that not everyone cares to own a dedicated jump cue. Fact is, any cue can properly jump a CB and a JB will help you jump even easier than a playing cue simply due to it allowing you to hike up the shaft higher. Not everyone cares to carry around an extra shaft and handle either. Whether or not you personally choose to agree is besides the point. Facts are facts.
As for your last point, "Why would someone want a jump cue that doesn't jump properly?" Does this even make sense to you when you re-read it? You can properly jump a cue ball with ANY type of cue. People were jumping with house cues and personal cues way back before jump cues were even a thing. A JB cue CAN AND WILL jump a CB properly. In fact, by unscrewing the bottom part and making the cue shorter by itself will allow you to jump the CB easier than with a full length cue. All a jump cue does is allow you jump properly with much greater ease.