That's not the same thing. They're artificially limiting one component that's perfectly capable of functioning at peak performance to hide the degradation of another.

If your battery starts degrading while still under warranty how would you know other than "hmm... my phone feels slower than usual".

How does this throttling occur? Is it gradual or does it happen in large noticeable steps? My guess is that it's gradual throttling because it's taken this long for people to identify it.

Does the throttling only occur after the phone is out of warranty? Or is Apple hiding a potential warranty repair?

Do you think the ECU doesn't limit the performance as the engine ages to protect it from damage? Of course they do, just swapping the ECU in an old car for a brand new one will restore some performance, because the ECU starts supplying the stock levels of fuel/air mixture, at least until it learns that the engine is not performing as expected and cuts down on performance again.

The ECU isn't intentionally degrading performance, it's balancing the air to fuel to compression ratios for optimal combustion of fuels and reduced emissions. It's a dynamic systems and degradation in performance occurs as a result.

It's not intentionally handicapping the performance to hide the fact that your fuel tank can no longer hold the same volume of fuel.

And Apple is balancing the battery's voltage level with the CPU utilization for optimal reliability of the device.