Future stars seems to be a huge boost for the younger kids - especially if its the way to get a kid working more progressive drills/skills at a younger age. In our region, those kids clearly show a huge advantage through about L7. Hard to say higher up - here there are few kids in the top levels....
My oldest boy has made HUGE gains gymnastically with the onset of puberty. He started competitive gym late (almost 11 - although he had played around with rec gym enough that he competed L4 successfully 6 weeks after starting). He then spent 3 year as a L5 before things clicked, then skipped L6, is competing L7 while having his L8 routines mostly down and working on L9 stuff this year...at 14. He probably never would have "made" it in future stars had it been an option as a youngster...he wasn't interested in working hard on gym and didn't have the obvious talent until about 10 1/2 years old....but he has not intention of college gym - although he thinks it looks like lots of fun...before puberty he never expected to make it past L7.....
The few kids who have done Future stars at our gym were amazing - one nationally ranked for years - and it kept him in gym. 2 others could have done it, had no interest and have moved on to other sports. We have a little 7 year old who would have been a good L5 this year, and benefited from future stars, but because we can't do that program until we have a full time experienced head coach again, he simply moved to L6 and has had a "terrible" year score wise, but is at least working with the more serious kids and working on progressive skills in the areas he's ready to do so.....and he's happy and enjoying the meets anyway, so its worked out in that sense.
My guess is that if a kid is getting good solid training in fundamental skills and staying interested in gym, then unless the goal is the Olympics, its more important for boys to simply STAY IN GYM until they hit puberty and see what it does for them, than push hard when young - but Future Stars really does work those fundamentals well. It would depend a great deal on how much more time would be involved - our nationally ranked Future Star kid never trained more than about 16 hours a week even as a L9 this year - So many talented boys simply move on to other things.....