I was told by a guide but still can't be sure, that when you delete a crafted item, that it gets stored in a kind of trash file and every so often, the server puts back to the junk piles as it prunes the file. DOn't know if it's true, if what you toss effects what is put back since what you get from trash is random of 4 resource types. But if it looks at what is trashed then grinding stone tools won't help build up trash because they don't use trash piles.