We still don't know exactly how the human brain works. But what we do know is that it is analog and not digital.
Some speculate it may even be quantum in nature. And we know that quantum can address problems that are intractable with digital computation.
For all we know, "intelligence" could be an inherent attribute of the universe that is being manifested somehow in the human brain.
In the context of existing AI "computational" models, it does. It's all we've got.
"But mindcrime, there's a mathematical proof. How can you argue with math?"
To be fair, I didn't read their entire proof. I skimmed some bits of it, and while I can't say it's wrong I didn't find it very convincing at first blush. My initial read left me thinking that the proof rests on some assumptions that may be unfounded and which may not hold up.
Some of my skepticism may also be rooted in the way the paper seemed to weave back and forth between claiming to show that "AGI is computationally intractable" and "AGI is unachievable in the short-term". Those are two substantially different arguments and it's still not clear to me which the authors were really aiming for.
I dunno. I gave up before getting through it all. I'll wait to see if others find it compelling and decide whether or not it's worth going back to.
Also, see earlier discussion: