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".