Yes, I am aware of that. And why. Ruger has no choice in the matter. Converting three screw Rugers to the new model type (transfer bar), no matter what the customer wants, is something they are legally bound to do. It was part of the settlement that created the New Model lockwork. If they don't do it to every 3 screw they get, they are in violation of the terms of the settlement.
They used to return the old parts, I am unsure why they no longer do, but it is probably to avoid some possible legal entanglement.