You will find many on this site who agree with you about the balance point being bogus and even more who agree with you about using the core.
My first reaction is that I agree with the intention of the "lead with the heal" teach as it promotes staying closed as long as possible. However, to have all of your players "round out their stride" seems a bit cookie cutter-ish. Ultimately, you want the core involved and you want good timing. Rounding out the stride actually makes the stride take a bit longer. But there are other ways to adjust timing (e.g. lift the knee to the back shoulder or even back towards 2B). So my suggestion is to be open to different ways of achieving your ultimate goals. What works well for one pitcher might not work as well or even at all for another pitcher. Keep your options open.
And it gets harder the older the kids are because it's even more engrained in them. Two drills I would suggest are the Hershiser drill and the Crossover drill. These come from the NPA and teach leading with the hip to create early momentum. I'll try to get back on later to describe these or search for those drill names in old posts by me - I know I've described them before.