Point being: what you end up with if you go down this road is not a copy of a human mind: It is almost immediately a neuromorphic entity.

People who have thought about this seem to mostly think that a lot of things would change quickly - I suspect any disagreement you have with Bostrom is about whether this creature derived from a human is close enough to a human to be thought of as basically human-like. Note that Bostrom thinks of the space of possible minds as being vast, so even a very weird human-descendent might seem basically human-like.