I agree that historical fiction requires as much imagination as contemporary fiction - I'm not sure it's more or less. I do agreem though, that you have to exercise your imagination withing greater constraints since the facts have to be eased into the fiction and you start off with a larger body of knowledge tp consider.
Depends how you apply the demarcation between fact and fiction. Arguably historical novels, for instance, require as much, if not more, imagination than fiction, since one is obliged to place his or self into situations that haven't been engineered for the narrative. Accordingly, the constraints of fact prompt the writer to think things through, project, imagine, things more thoroughly.
I reiterate the phrase 'arguably' as, like any discussion, the key factors here are the justification of one's opinions.
