I agree with the PP about using more influences for drama than just the Tudors/ Queen Vic. There are so many interesting sources of folklore, historical perspective and human interest than just British rulers from ages ago.
I also think that a fictional character (whose race is not key to their part e.g. not a Klansman) should be open to the best actor for the part, even if they are a very well known character such as Ebenezer Scrooge.
However, for a real character, certain things about the actor's physicality will tell parts of their story, so Anne Boleyn would not have married Henry VIII had she not been quite a young woman at the time. Therefore unless it was an experimental/ non naturalistic piece, it wouldn't make sense to cast a man or small girl.
In terms of race (and I know not everyone's race can be distinguished just by looking at them), If Anne Boleyn was black, it would infer a different history, heritage and story to the one we know about and I'm sure is well recorded.
So i don't agree that it's just about not looking much like Anne Boleyn and that not meaning anything. I very much see the reasoning behind casting an actor who is attractive by today's standards as Henry VIII as presumably he had something going for him back then!
As much as I agree BAME actors should have equal access to work and good parts, I feel that in a historical/ biographical piece, we should recognise that personal characteristics play a part.
For instance (and I'm not suggesting that white actors face the same difficulties in getting parts), I don't think anyone would argue that in a straight drama/ bio of say, Michelle Obama, the lead role should go to anything other than a black actress. Why? because race isn't meaningless. I feel we need to try and achieve parity, not erasure.
Obviously this is no comment on Jodie TS's abilities. I haven't seen any of her work but have no doubt that she is very talented to get the part.