I think there is some truth in that and this final run of Stranger Things may be an exception but, I am watching the latest season of the The Morning Show and so far episodes are approximately 50 minutes in length.

Sure. But I suppose I mean historical TV shows tend to be between 40-50 minutes where as 'prestige' is usually 50-60 minutes in length.

But the historical TV shows tend to be 20+ episodes a season.