In case anybody (like me) wonders where this information was taken from and if it's accurate, if you check https://www.irs.gov/pub/irs-pdf/i1040gi.pdf page 14 it states under married filing separetely section:
"If your spouse doesn’t have
and isn’t required to have an SSN or
ITIN, enter “NRA” in the entry space
below the filing status checkboxes"
