Versions 3.7 and below are all in feature-freeze, so this change could only apply to 3.8 and above.

I don't know if this feature is desirable or not.

If it is (sometimes?) desirable, my guess is that it would be undesirable to use SUDO_USER *unless* the effective user ID was 0. (Don't check for the name "root", that's only a convention.) In pseudocode:

    names = ('LOGNAME', 'USER', 'LNAME', 'USERNAME')
    if effective user ID == 0:
        names = ('SUDO_USER',) + names
    for name in names:
        ...


Also needs documentation and tests.