Yea, in my mind it's more of a case of, if we get to the point where we can simulate one brain properly in this fashion, it's essentially useless.

We can simulate the brain of a Lithuanian man who has been addicted to 2CB his entire life. Great. Now that we have done that, we have essentially just recreated a brain that already exists.

What does this fake brain tell us that we don't already know, after studying this man for his entire life to determine all the inputs required to simulate his brain?

We now have one brain. This is useless in an inferential sense for any kind of research - we have a sample of N = 1, meaning we have a case study of a brain that we already have fully mapped without having to expend the resources to simulate it.

Once we have the capabilities to simulate a human brain properly, we wont need to do it (or learn anything substantive from it). This is the argument I most agree with anyway.

I wouldn't be so quick to distinguish between a biological brain and a computerised one, they exist on such different planes that (in my opinion) such broad statements are bold to say the least. I do appreciate your point though.