It's indeed quite possible it is not reproducible by building digital computers out of silicon, sure, but that does not prevent us from picking another way of building them.

I'm very much sympathetic to the idea that there could potentially be aspects about the specific structure of a brain that is necessary to produce intelligence, or at least necessary for sentience. But does not inherently make it impossible to reproduce. For it to be impossible to reproduce a brain, there would need to be something in the cellular machinery used to construct a brain that we can not pick a party and replicate.

As a reminder, the argument made in the article is that it is impossible even in principle, not that it is impossible to do it using a digital computer of typical current architecture.