But I am talking about the Mercedes team and the Red Bull team's ability to produce the fastest car for both their drivers.I don't know what you mean by true speed. Or I do, but it's just an average of how fast these two specific drivers are capable of driving the car, not an estimation of how fast the car is (especially in comparison to another car). How fast the Merc is doesn't change just because Bottas isn't able to keep up with Lewis, so all you're really saying is that Lewis can drive the car faster than Bottas.
Lewis and Max are driving closer to their cars maximum potential than their team mates which means their times are the most accurate representations of how fast the cars are. It's not a perfectly accurate representation since in theory either driver could be getting more out of a slower car, but I think it's pretty safe to say that both of them are very close to extracting the max from each car.
I think that's more a case of him pointing out that even though he didn't do a perfect lap he still got pole, not that he's not capable of driving the car as fast as it can go.
Anyway, it is academic.