Edward Mordrake: Part 1 - S4-E3
Deliberate mistake: After Elsa kicks Bette and Dot off the stage, Elsa looks at the sheet of music on the stand and you see the name of the song 'Criminal' and it also states it's by Fiona Apple which is true, but this season is set in 1952, and Criminal wasn't released until 1996.
Answer: Moira's ghost form is unique because of the way she was treated when she was alive. To people who do not sexualize her and truly understand and view her for who she really (namely women), she is seen as an older woman. To people who objectify and don't care to see the truth (namely men), they see the young seductive Moria. It's a strong directorial choice to eventually show how Ben Harmen comes to terms with the truth of the house and himself.