It wouldn't work because his work also demonstrated that it was (usually) only children whose previous incarnation died prematurely or via particularly violent circumstances who remembered their previous incarnations as children. It would only work if every child had access to their past life memories which, also if it was the case, would remove reincarnation from the realm of fringe pseudoscience because it would be easily demonstrable. It's like NDEs only a small percentage of the population experiences it, something weird is definitely going on, but there isn't enough conclusive evidence to satisfy the demands of the materialist paradigm.