Agreed.

I think there's another layer to this too, which is that — if you've already scanned and uploaded a person's mind, the original person is presumably dead, or at least a completely separate person from the one in the simulation. Moreover, really, no matter how much versimilitude you pour into your simulation, it's never really going to be exactly the same. Hence, if we're being clear-eyed about this, presumably the point of doing a brain upload like that isn't to get immortality for a particular person or something, its just to get a much more advanced and human-like form of artificial intelligence.

At which point, if we don't need a perfectly accurate neurological and physical simulation to get something that mostly "walks," talks and acts like a human, or something very similar, why would we bother doing it at all?

And yeah, although you could obviously assume that perfect simulation of all of the physical and chemical and neurological processes is necessary to get something to even slightly functions, considering the fact that people can function with 90% of their brain entirely gone, I'm not sure how accurate that is.