Isso parece ter sido negligenciado:
Defaults umask_override
que faz o que foi perguntado (veja o sudoers manpage ):
umask_override
If set,sudowill set theumaskas specified bysudoerswithout modification. This makes it possible to specify a more permissiveumaskin sudoers than the user's ownumaskand matches historical behavior. Ifumask_overrideis not set,sudowill set the umask to be the union of the user's umask and what is specified insudoers. This flag is off by default. If set,sudowill run the command in a pseudo-pty even if no I/O logging is being gone. A malicious program run undersudocould conceivably fork a background process that retains to the user's terminal device after the main program has finished executing. Use of this option will make that impossible. This flag is off by default.