Should be a switch in the settings. Prefer battery life or prefer performance. One more setting won't kill anyone.
They can throttle the chip to what the battery can deliver or it will crash. Maybe Apple's more conservative on the throttling, and some amount of performance could still be achieved without a crash, but there's zero chance Apple's putting a "make my phone unstable" switch in Settings.
Over the course of many discharge cycles, the battery will lose capacity, and the point when the voltage is no longer sufficient to power the phone will come sooner.
But this is overly pedantic. People generally consider this point to be simply an "empty battery."
Android phones do not suffer these performance changes. Instead, the phones lose battery life over time, and within a year or so, you might be lucky to get 12 hours of life out of a full charge.
You can make an argument that we should optimize for duration or performance, but the difference is that casual Android users are aware that their battery is deteriorating, while casual iPhone users believe their phone is itself deteriorating, or else much slower than the newer models.
It's not just smoothing out a peak demand. It's reducing the peak performance all of the time, and that is unique to iPhone.
Mine runs at 50% CPU speed under those circumstances. I wouldn't call that "performing as expected."
So throw in a fat capacitor. This was a solved problem 50 years ago, the only problem is this constant rush to make phones 1% thinner.
I've never met anyone that used phone thinness as a metric when choosing a new phone and yet here we are.