They dont show that. They show 20% more PR. That is not the same as 20% more productivity.

You just compared this AI shift to "tractors on farms". Did tractors increase farming output by 20%?

The first tractors in 1911 or whatever probably did. 50 years on and it was many times that.

No, at least not if you're talking about tractors broadly. The first practical traction engines (~1860) were pretty much instantly revolutionary.

I suppose you could make the claim that the first things commonly called tractors (which were petrol-powered) might not have increased productivity very much, but "tractors on farms" should surely be read as the revolutionary moment, not the change in dominant fuel type 50 years later.

Also, it's likely not safe to read "20% increase in PRs" as "20% productivity improvement".

You don't get paid 20% more for achieving 20% more achievement, that's for sure.