Somehow this article seem to make the mistake that "experts" are all just spending their time making predictions, and not spending anytime doing research and experimentation to acquire more data and evidence.
Most experts in most fields spend their time doing research and experimentation, in order to acquire knowledge and build a corpus of understanding that makes that 99.9% into a 80%, a 50%, a 20%, a 1%, etc.
The only "experts" making projections tend to be fake experts, they'll actually be policy makers, investors, marketeers, etc. (yes sometimes they'll hire an expert statistician to waste his time help them with such foolishness)
And ounce those people enter the game, they'll pester the real experts ad nauseam for estimates and for predictions, and at first the expert will say well more research/experimentation is needed. But the fake experts will say, ok, but ballpark, just an estimate, what do you think is most likely happening here? So the expert will say, ok, give me some time to really run the numbers and make sure at least I'm giving you accurate statistics. But the fake experts will pester some more, I need it by end of day, just tell me now, why would it take you so long. Eventually the experts will just make it up so that the fake experts leave them alone and they can go back to doing real work like research/experimentation/development, etc.
And this in my opinion invalidates the claims in the article. Because those experts cannot be replaced by a rock. The reason they'll be doing the same work as the rock, is because non-experts are going to want them to do so, by asking them the question the rock could answer, and refusing any answer that is probabilistic, they want certainty, not possibility. And to those people, it matters very much that the expert said so, because in the expert they trust, in the expert they can scape goat their failures, they did not make the decision, the expert did. A rock does not provide them with plausible deniability.