Normally the better boxer always does better, makes adjustments and wins in rematches, there have been many examples in the past of this. So was this the case for the Canelo/GGG rematch?
Regardless of ones' specific scoring, I'm not sure very many people thought it would go down the way it did and that includes everyone emphasizing the point of the "better boxer" winning rematches.
I thought Duran, Hearns and SSR were pretty good boxers. They didn't always do better in their rematches, sometimes clearly worse.
Robinson was a classic case of adjusting after a loss, Turpin, Basilio both got worked out after out boxing Ray.
I'll throw a name out there, Orlando Salido. Why come Juanma didn't win the rematch? I'll throw another name out there, Leo Santa Cruz. Why come Frampton didn't win the rematch?
But not in every instance. He had a number of opponents he did worse against (lost) in their 2nd meeting, like LaMotta and Pender.
I don't know Gonzales didn't do better with Rungvisai. Mosley didn't do better with Forrest. Oscar didn't do better with Mosley. Groves didn't do better with Froch. Barrera didn't do better with Poison Jones. Just naming a few.
??? Have you watched the Turpin - SRR rematch? Ray did anything but 'work out' Turpin! He got roughed up for a second time and had to go for broke having been warned he might get stopped for his own good due to injury. SRR was such an outsized talent he dredged up a fight-ending barrage from the soul of his boots! It was anything but a masterclass, tactical clinic which you comment suggests.
As for GGG, he did improve the boxing tactics and so made up for his physical decline, beating Canelo slightly more convincingly than last time.
Oh, you mean like Shane Mosley vs Vernon Forrest, Manny Pacquiao vs Juan Manuel Marquez, John David Jackson vs Jorge Castro, or Ivan Calderon vs Giovanni Segura?