When the program was created, there were no restrictions in Windows for where to store files that programs wrote to and it was common to store .ini files in the Windows folder. This practice is no longer observed and Windows is now a protected area.
If the user is running as a Standard User, Windows 10 redirects disk writes to protected areas (such as Windows) to the virtual store for compatibility with legacy apps. This means the program will function as if it’s writing to its original location even though it’s being redirected.