I think the original post hits on the answer to this question. Junior OW... same training as regular OW, and the course has the same objective: allow younger people to qualify as OW divers. The same principle for JAOW, Rescue, etc.
PADI knows that the title "Divemaster" has a powerful marketing draw. How often have we encountered excited new divers who insist they want to be divemasters? When asked about their plan, their motivation, we find it's usually because... it "sounds cool." And they're excited about diving.
No one objects to teenaged divers having access to this training. I think the objection is mostly to the perceived deception: a Junior DM cannot perform many of the primary functions of a standard DM.
Once could argue that the JDM training provides a pathway to full DM training. While this is true, it does not require that the Junior program be called "Junior Divemaster". In the standard DM course, divers can be given credit for certain portions if they have completed the Deep Dive or S&R specialties. So there is already precedent for training outside the DM course to be used as part of the DM course. If the intent of the Junior DM course was truly to provide teens with practical training that could then be applied to the full DM course, the Junior course could be called something else... just as the Deep and S&R specialties don't mention "divemaster".
So back to your question: no one is objecting to the training; the objections (as always... this is not a new issue) are to the perceived money grab by using the label "divemaster" where, it could be argued, it's not appropriate.