Is it okay to write "non-resident" for non-resident alien spouse's SSN?

I live outside the US with my non-resident alien spouse. I want to file as married filing separately. However, in online tax preparation software, it always forces me to enter an ITIN or SSN for my spouse, even if she is a non-resident alien. Is this really required? I saw an article on HR Block that says “The nonresident spouse isn’t required to get a taxpayer ID number. You can put “NR” for your spouse’s tax ID number on your return.” That would be very convenient as I wouldn’t need to apply for her to get an ITIN. However, on this IRS website page, there is a line that says, “If your spouse is a nonresident alien and you file a joint or separate return, your spouse must have either a Social Security Number (SSN) or an Individual Taxpayer Identification Number (ITIN)”. Nonetheless it seems a little strange that a non-resident alien spouse with no US income would need to apply for an ITIN just because she is the wife of a US citizen. Even if I file separately, do I still need to enter an ITIN for my spouse? Or can I just write “NR”? Thanks.