Imagine if ford started to detune your engine as you added miles to the car, but DIDNT TELL YOU. You lost X horsepower every 1,000 miles.
You do lose X horsepower every 1000 miles. You get it back with your tuneup. Which involves changing the oil.
You lose X MHz every Y% of battery discharge capacity lost. You get it back with your tuneup. Which involves changing the battery.
You don't need to detune maliciously to get the effect Apple is getting here. The system just needs to self-calibrate to a depleting battery... Which is super good for the battery because it won't actually get worse as fast. Discharge cycles, especially close to the discharge limit, puts strain on cells, which have voltage sag closer to end of life.
My iPhone X is 3 years old, and feels just as fast as when it was new.
If you want a reference that proves that NAND performance degrades over write cycles: then I will only list one, but there are hundreds, at least.
But is there any evidence that translates into an appreciable impact on device performance?
Perhaps it doesn’t, and this is why nobody is talking about it.
Again, this is all semantics. The whole point is apple never told people they were throttling. And you've got two groups saying "Oh they are so nice, they did it so you could keep using your phone, how nice of them" and then the "my phone is slow I guess I need to buy a new one".
Would you guess, this is actually what's happening.
ECUs constantly adjusts for current conditions (EGR, variable gem turbo, o2/fuel ratio, fuel inlet timing, combustion timing, variable cam timing and phase, knock sensor...). As the engine is used, wear makes its performance degrade over time, and the ECU adjusts in real time for that. Maintenance such as timely oil change mitigate that, some parts may have to be replaced at some point (from spark plugs to turbo), and over time the engine itself wears out.
Here's a very specific example: all those cars with hypermiling downsized engines turbocharged to compensate perform brilliantly, but when the turbo is dead they can barely crawl themselves in 1st gear. In less extreme situations, turbo wear will put you relatedly anywhere within that [perfect, broken] range, and the ECU will do its best to compensate, unbeknownst to you.
It's more like, "Imagine if for reduced horsepower when your engine was at risk of overheating, and would not function properly at the standard horsepower".