Windows actually uses SIDs to map internal users to windows settings such as profile locations and group policies. Open regedit and under HKEY_USERS there will

Windows actually uses SIDs to map internal users to windows settings such as profile locations and group policies. Open regedit and under HKEY_USERS there will be the SID for your user account which maps to HKEY_CURRENT_USER. Linux has UIDs that map to the username. Both methods allow for changing the user name without having to change permissions on files. Both need manual manipulation to transition the user's folder name to the new username. Both also allow for creating a user folder that does not match the username. Example HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList on Windows. Best practice and reality are two different things. Even Microsoft often will use the fully qualified user profile path in their coding instead of %USERPROFILE%, example would be OneDrive. Just look at the Environment key in regedit for the current user.