Valteri is good but Max is great. It was an optimistic call by Mercedes and traffic ate up whatever wiggle room they had in their strategy. Also, Max was probably pacing a bit due to the large gap to Lewis, and had more in the tank that the Merc. strategists factored.
Remember, Bottas was told he had to run 1:18.5s to catch him quicker than he actually did, and he did run those times. I don't have the lap times in front if me, but a quick look shows Valteri was overall faster than that. Someone should take the average from that point (radio transmission) to the end and that will tell you. If Valteri was faster than that, he exceeded expectations and it was the strategists who got it wrong.