This might be arguably true for the 1st generation, the one who becomes a noble. Maybe this noble marries another 1st or 2nd generation noble and they have children who are also pretty great. But regression to the mean indicates that, at best, future generations will inevitably be average, and half will be below average. Especially, and this cannot be over emphasized, when they interbreed.
Add into the mix that nobility is conferred via political maneuvering, and it's not guaranteed that even the 1st generation was all that notable
Plus I would also argue that successful political maneuvering is a sign of superior fitness.
Ok? You didn't really explain why. Surely by extreme you don't mean "being noble". You're asserting that 2 nobles will have a child who is "extremely noble"?
Do you also believe that 2 rich people will have a child who is, genetically, "extremely rich"? That over generations, these descendents will just be inherently richer and richer?
You can imagine this as a form of de facto rule.
