From an actors point of view...

Is it no longer acceptable for a team of creative artists to develop a dramatic interpretation of a historical fiction. One that has conflict, human weaknesses, social historical context etc.?

Without conflict there is no drama. Without drama there cannot be a climax and some form of resolution. In this case, the story is not written with the alleged rape of the Duke as the center of the plot. It is written to be much more indeterminant and complex. This allows the relationship between the Duke and Duchess to further develop, some might say, mature after the event in question.

Finally, it stretches credulity to think, in this specific instance, that the Duke, had he wanted, could not have physically decoupled given his strength and size. That he did not would suggest he was at the very least, torn between his principal to deny his dead father an intact bloodline and his passionate love for the woman he married.

Now, that's good drama.