I am disappointed that this question did not get the same label.
It's a bit idiosyncratic depending on the individual mod who applies it, but in general we try to use the flair to highlight questions that apply to under-studied groups of people, things that aren't our usual run-of-the-mill questions, and so forth. My rule of thumb that I will apply it if I see a question on women's history, Indigenous history, Black history, the history of ideas, and that sort of thing, and will never apply it to questions about Hitler, WWII, ancient PTSD -- basically anything that's in our VFAQ.
You might like reading the thread announcing the "Great Questions" flair from /u/Georgy_K_Zhukov
See also the previous meta thread Does marketing questions as GREAT QUESTIONS subtly bias which questions get answered? Does it make people feel uncomfortable because a question not marked can be implied as a average/below average question?
/u/crrpit
Solid question. Very interested to know what the moderators say. (And im what manner they do so).