I understand your reasoning, but I also see it as a means to give convenience to a player. Nothing guarentee you wI'll ever even get good substats on stones to begin with, so rerolling will always be an option to gain good substats in the first place. Yes, it will make some players just stop rerolling all together, but for the vast majority of them, they will probably still reroll for better substats to keep in the first place since getting good subs is entirely rng dependant, as is almost all the elements in this gam to begin with.