This will avoid effects being unexpectedly broken in these games if the user disables the option globally. This list is by no means comprehensive, these are just the games I could confirm use custom mipmaps.
Having settings for each game in more than one file is redundant.
Now, region-free INIs are now only for settings, and region-specific
INIs are only for AR codes and patches. Exceptions are made for
titles that share the first three characters of their IDs with
unrelated titles (mostly unlicensed titles and Triforce titles).
Techjar