At first, I thought they were only added members of the Old Republic under the tag, not just everyone alive during the OR era.
Then, they gave Fallen Bast the title, which breaks the trend, because at that point, she is no longer a member of the republic (unless something in the dark side route says otherwise. I never played the dark side route)
While I think HK deserves the tag because t3 has the tag, I can see reasons for not having it- HK a lot more independent than t3, so loyalty to master didn't mean loyalty to master's nation. Or, it could be a version of HK during Kotor days, while he served the Sith Empire. Or even the time in between when he was just wandering in space