Is whitewashing a two way street?

I was recently watching this video about whitewashing in films, and it started me on a chain of thoughts that I'm slightly confused about. I'd like to get some alternative viewpoints on the matter, to hopefully clear up some issues I'm having.

In this video, the person presenting the opinion goes on to define whitewashing as:

[...] when Hollywood takes a character who is a person of colour in the source material, and casts a white actor for the final portrayal we see on screen.

This definition is good, and I agree with it. I can also clearly see how "Whitewashing" is a problem. However, later on in the video she says:

But this thing some people like to call "Blackwashing", is not a problem. It's not even a thing.

This is what I have trouble agreeing with. If we take the definition provided for whitewashing as a good source, how can "blackwashing" not be the opposite, where a person of colour plays a traditionally white character?

She provides some examples from comic book movies, such as Nick Fury from the MCU. I think that Samuel L. Jackson does a great performance as Fury in all the MCU films; I wouldn't cast any other actor for the part. However, I do have a problem accepting that "Whitewashing" is a problem, but "Blackwashing" is not. Logically, would not either one or both of these be a problem? I'd love to hear what everyone thinks about this, as I'm pretty clearly confused myself.