@xinya I think "Mr. Queen" was moved to the period list after one of my comments. Even though the drama is set in Joseon era with characters based on real historical figures, I thought that the time travel and body swapped plot made it far different than a "traditional" historical drama because the character who travels through times has conscience that he is not living in his right time and have knowledges over things that people in that era couldn't maybe even think of, which is, at least for me, far different than a story set in a specific era, with historical figures, but a lot of adaptations and liberties regarding the characters and the events. The time-travel element is kind of similar to making a drama with historical figures having magic powers for me, it changes the "reality" of the drama totally, on a different level.
For exemple, the recently finished "Bloody Heart" is purely fictional, but for me it's an historical drama because there is no "external" elements to the era the story is set in.
That's why, for me, in the Historical main genre, everything that is truly part of the historical sub-genre too (with sub-genres like Historical historical, historical fictional, historical adaptation kind of ^^) is only stories that are set in a traditional historical set without "non-natural or unrealistic elements", even if historic events and figures are adapted or changed a lot, and everything that goes to period dramas and other sub-genres is basically the rest.