krtek a houby
Merry Xmas!
My take on the Cushing Doctor remains. It's an inventor bloke like the fellow in the HG Wells story and his adventures take place in a parallel universe.He could be suffering from regeneration sickness that makes him think he is human. That half happened to no 8.
That or he is deep undercover pretending to be human. They did that before too.
But your canonical reasoning also makes sense.