You have to uncheck the rename on disk... rename only in session.
This simply changes an attribute and you have to save the part to have it remain.
The whole rename let you optionally keep your current files in tact. If you have an assembly or drawing open, for instance, you can swap out a part. But the whole dialog is somewhat archaic. I often have to do what you are doing in two steps... rename the part, and then rename to common name. Silly, I know.
