I had read that before, and am trying to understand. After one installs the games to program files, these do not change again until addition of another EP/SP, yes? All the information that changes as you have a play session is saved to the local game?
All mutable files are supposed to change only in the user directory. The core files are not altered except by patches or possibly new expansions.
Please forgive, as after reading many, many posts, sometimes the information seems to conflict and I hadn't set up a new game in a long time. I read one post that said the person found 15 packages to change, another elsewhere said that information gets written to the packages.
It's not SUPPOSED to be! That's sort of the entire point of denying write permission!