Well we don’t know the full scope of what creates consciousness. Even if we replace our neurones synthetically, and copy every function they have so they they act as they would do if they were biological, there’s no telling what mechanisms could be lost in removing the underlying biological process itself.

For example, if consciousness is a byproduct of finely tuned entangled systems induced by our hormones and the many chemicals flooding our brain, then removing that and emulating the effect synthetically without the cause, may cause a collapse of consciousness.

I wouldn’t hedge my bets either way, but I think there’s a lot of room for discovery still, and it’s not as simple as merely synthesising the brain.