Purity On Rubble?

On the salem wiki it is said that purity of any roasted meat effects the lard gain chance and that the base is 3%
Is that actually true and does this also effect the chances of getting goldflakes/blacksand/gems when sifting? Or the chance of getting sterling geodes while chipping?
Is that actually true and does this also effect the chances of getting goldflakes/blacksand/gems when sifting? Or the chance of getting sterling geodes while chipping?