I have no idea how the premium version differs much from the free version at the moment since the current version is almost exactly the same as the free version.
What differs from the free version? Only two things: showing the last CG of the chapter with the sprites of the Priestess and Zero blocking the CG and every ending is Six asking to buy the Premium version.
So, either the problem wasn't fixed or the wrong version of the game was mistakenly updated and then uploaded instead.
I would like to read the extra content, so I hope the problem gets fixed.