The problem with this wacky theory is it de-emphasizes full adulthood for the species, and survivability to old age is no longer an evolutionary plus. Essentially, this type of reproductive model would result in inevitable alteration of the species over a short period of time due to reproductive pressures, with an emphasis on mutations that expand or enhance the reproductive advantages of its youth. Features prominent in full grown adults such as size would become vestigial.
The only explanation for such over specialization that I can see is that the species had a complex social system where the full grown adults enhanced the reproductive advantages of the younger individuals by caring for, protecting, and feeding their offspring’s offspring and/or genetic descendants. But the gist is that the reproductive period would naturally increase over time as those who remain capable of passing on their genes the longest are more likely to have more offspring. Such changes in physiology over time would have other effects on the species later development.
I guess what I’m saying is that such a reproductive model is inherently unstable and any species which has such a model would either become extinct due to overspecialization or will become a candidate for inevitable and rapid evolutionary change... resulting in extinction for the originals.
Your comment makes sense to me. Thanks.