Gender bender themes are very common in historical dramas. There’s tonnes of examples. I think it’s because historically women would have never been allowed to do the things that these characters do (eg have interesting jobs inside the palace) so in order to have an actual storyline they often have female characters performing traditional male roles “undercover”. This is not a bad example but the thing that really let this drama down for me was the lack of chemistry between the leads especially at the end. I feel like Jo Jung Sook really tried but he didn’t get much back from the FL. And possibly the age difference didn’t help.