In Hansel and Gretel, I am not sure if the standard version has the parents abandoning the kids twice but I think so and the second abandonment (or the first) is simply omitted with Hans leaving a trail of breadcrumbs which are eaten by birds whereas the first time stones were used effectively.
I realize the Grimms had many arbitrary and often simply nonsensical (as well as cruel and outright antisemitic) plot elements so perhaps there is no explanation for Hans choosing to leave breadcrumbs but maybe this can be explained?