Renaming Theme in Source Code

Hello,

I've installed the GeneratePress theme and the GP Premium add-ons. It seems in order for me to use the Premium plugins, the theme folder cannot be renamed on the back-end? I tried and it said: "To use GP Premium plugin please install GeneratePress".

Note: I still changed the stylesheet, screenshot, and name of the theme on the WP-admin. But on the source code, it's still 'GeneratePress'. I realize keeping the original name on the back-end makes sure you get automatic updates, but I would like to rename to a custom name, is this possible? Was I doing something wrong?