"But how is this different from an African-American actor playing an early 19th century Eponine of Valjean?"
I doubt that this could be explained to your satisfaction via this medium, but suffice it to say that we are not yet at a place in our evolution where roles of color can acceptably be assigned to white actors. At least in the US and Europe, that is - I doubt if anyone on this board has any interest in questions of racial casting and portrayal in Asia, the Middle East, Africa, or Latin America. In fact, there may be many who think that racism only happens in countries with a white majority or hegemony.
I doubt if anyone would see any problem with a production of Othello in Japan, with a Japanese actor playing the title role, an attitude which is, I suppose, just another face of racism itself.