Disappointing answer from Apple. The 2011 MBAs were Core i5s and i7s, not Core 2 Duos. :/
As I've explained in my earlier posts, the idea of measuring these new Core processors with one clock speed number is misguided. Rest assured that a 2015 MBA is significantly faster than your 2011 MBA.

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Okay, I'll bite. I read the web page and it agrees with everything I've said.
It says "amount of time the processor spends in [turbo boost] depends on the workload and operating environment."
It goes on to specifically say that it will turbo boost as long as power consumption and temperatures permit.
I have maintained from the beginning that the MBA has enough thermal headroom to maintain max turbo boost speeds indefinitely. And it obviously has enough power headroom since the laptops haven't changed their power/cooling situation for ~5 years, and chips 5 years ago used way more power and produced way more heat.
If you monitor the CPU temperature of a current MBA under full CPU load, you will see that the fan only spins up to around 4000 RPM with ~70F ambient room temperature. The max fan speed is over 6000 RPM, so clearly there's thermal headroom to spare.
So what I've been saying agrees 100% with your web page.
And regardless of your opinions and "understanding" of turbo boost, it's trivial to download Power Gadget (it's free) and load down your CPU. You can probably confirm everything I've been saying in a matter of minutes. No speculation required.