I have other account name for user with uid=0, not "root".
But this name is hardly encoded into source.
I think, it is in file testsudoers.c. There is line:
user_name = argc ? *argv++ : "root";

Other programs, ex. "su", work correctly with other than "root" account name. They check for uid=0, not literal name.

Can You, please, add to "sudo" ability to automatically find literal user name with uid=0.