No, It's just some option for other games.
For Warband it just happen with rgl_config.txt .
When I changed render_buffer_size to 500 and play Warband, then exit and go to rgl_config.txt again, render_buffer_size become 15, as if I've never canged them.
Another game that I have encoutered the similar problem is Assassin's Creed 2.
Brightness, mouse sensitivity, and subtitles option will be reset to defult evertime I closed the game.