Nothing is preventing anyone from hacking Stadia either, but the percentage of people who jail break their consoles is really low due to the complexity (most aren't techies), the amount of work involved, and because online multiplayer will most likely no longer work long term; or in Stadia's case - you can no longer access your games.

I feel the parent comment was referring to PC gaming, where you don't need to do anything crazy to customize the games that you paid for.