RC:

Just imagine this (caution: hypothetical numbers for understanding purposes only!): The 991.1 Turbo S produces 500 hp at 300 kph. Now what happens if the 991.2 Turbo S produces the full 580 hp at 300 kph? You get my point?

What happens is that while the Turbo S is making 580hp the 488 is making 670hp. And the McLaren 650S is making 650hp. That's why they are faster from 100 to 300. 

And the speculation that the 991.1 Turbo S is not making full 560hp at high speeds is ridiculous. If it's true, I will sue them immediately. Plus it's 0-300 time of 29.x - 30 sec matches perfectly a 560hp turbo car.