I can't be certain about that reason, but generally, it's not recommended to use Steam versions of older games for mods. It's better to get a pirated copy and apply patch 3.1 to it.
Added after 8 minutes
If that's the case, could you also suggest a mod for adding artifacts without having to go through a lot of trouble? Or is it impossible to do without a lot of trouble?
@AstralLein
