TIL my middle-aged ass isn't obsolete, it's just gracefully degrading.

Eats chips

I appreciate the thought, but I think you’re giving the concept too much credit, and also misunderstanding exactly what Apple did or why it was bad.

“Graceful degradation” is simply the existence of a wider range of failure modes. The flashlight is nice because there are more conditions where you can do something with it, but the life cycle of such a product is obviously not limited by the replaceable batteries.

Apple’s hidden power management hacks were also, in fact, an example of “graceful degradation”. As a lithium-ion battery degrades, high-amperage loads (i.e., the the processor when executing an intensive workload) will cause an increasingly large voltage drop. If the voltage supplied to the processor drops too low, the latches inside the processor will destabilize and begin to produce incorrect results (a 1 that should have been a 0, or vice versa). This is immediately catastrophic for obvious reasons.

Given this, you have two choices: either the device shuts down when the voltage drop becomes too large (at, e.g., 40% charge, depending on the specific properties of the battery), or you reduce the maximum current draw of the processor by reducing its clock frequency.

Apple chose the latter, which probably makes sense in the grand scheme of things. However, this was still pretty bad for two reasons: they didn’t inform the user that they were doing it, and first-party battery replacements were prohibitively expensive until recently. Because of this, most users would assume that their phone was slowing down because it was old, not because their battery could no longer supply adequate power to sustain the maximum clock frequency. Worse yet, even if they did somehow figure this out, it was rarely worthwhile to shell out the $130+ Apple was charging to replace the battery (which basically just involves removing two screws and a ribbon cable).

Apple, on the other hand, went out and said “if you don’t buy a new phone we’re going to make your old phone run slower”. I think the battery life was just an excuse - did Apple really think its customers would rather have a slower phone than a phone with shorter battery life? Sounds ridiculous.

This isn't how that happened at all and is an example of why this was such a bad marketing fail. Apple simply reduced the turbo just enough that the phone wouldn't hitch or power off when the battery degraded. It was such a slight change it was literally only noticable by a very small shift in benchmark scores before and after a battery swap. They literally did a good thing for device longevity and got raked over the coals for it

No it’s definitely about the flashlight more than the batteries. Most flashlights just have one connection/channel from battery power to bulb, and if this single circuit fails at any point then the flashlight is useless. This flashlight has four separate ones due to the layout of the batteries, and they each operate individually, so if one fails anywhere you still have 3 that function just fine.

How do you know if a battery has died? If three batteries have died and the flashlight keeps working as normal, then one day the fourth battery finally dies and the user is surprised to find the flashlight suddenly won't turn on. This sounds like using a normal flashlight?