In my experience, though, people now freak out if you fill in the SSN field on the form, because that makes it PII with a bunch of requirements for proper storage and transmission. This is despite the fact that most of the other information on the form already makes it PII, regardless of the presence of a SSN.

It did take a few years in the mid-2010s for the forms to catch up and replace the SSN field with the DOD ID number. In 2021, I think I was supposed to get new ID tags (dog tags) that would have my DOD ID number instead of my SSN.