This has been a phenomenon since desktop computer upgrades were first commonly available. Suddenly, Windows would be laggy after the 300 MHz "top of the line" processor seemed to be running at a half a cycle a second.
What in the world do you think "This phenomenon" has to do with the early days of desktop computer upgrades?
"This phenomenon" is hardware with such a weak battery that if the device runs at 100% power, the current drain on the battery loads down the voltage below what the device requires to remain powered and the device shuts down. A battery can only supply so much current, when you try to take more it's similar to partially shorting out the battery which lowers the terminal voltage. The chips inside the iPhone have a minimum required voltage and when you drop below that, the chips will not keep operating.
Modern CPUs use a highly variable amount of electrical power. When the CPU is mostly idling, it slows itself way down and draws a trickle of power. When it needs to do a major task, it ramps its performance way up and guzzles power.
Apple modified their phone software so that they would estimate battery health and limit how much performance the CPU could ramp up to to limit the electrical power consumed to be safely within what they battery could supply. Meaning your "300 MHz top of the line" CPU is suddenly no longer allowed to run faster than 50 MHz, for the sole purpose of making it consume less power.
The problem is that the battery selected by Apple is so undersized for the job that even in a phone a few months old would have such poor battery health that this throttling was needed. If Apple choose a slightly larger battery then the phones could go a coupe of years without throttling and there would have been no issues. Apple created this mess for themselves and their customers by choosing to make their phone a tiny fraction of an mm too thin to hold a proper battery.
[doublepost=1531139594][/doublepost]
If Apple really wanted to force consumers to upgrade they would only provide a single major OS update like most Android OEMs provide. What Android phone from 2013-2014 has the ability to run the latest Android without any modding? My guess is none.
Apple has redefined the OS to include a huge portion of the app base. Your iOS version determines your web browser, you version of pages, etc, and a ton of other Apps. This redefinition does not exist outside the Apple ecosystem.
To everyone who was using computers before iOS went to its annual update cycle, the "OS" was a thin layer of software mostly behind then scenes that would allow you to run the programs you need, support the file system, and take care of basic house keeping, memory management, etc. If you want a new web browser, you upgrade your web browser, if you want a new word processor you upgrade it.
The advantage of the non-Apple way, is you don't have to "upgrade" your entire workflow to have the latest OS and whatever features you do want. For example, I'm looking forward to the stacks feature on OSX Mojave. But to get that, I'm going to have to buy a new version of parallels, I'm going to have to upgrade iLife, and a ton of other stuff I may or may not want to. For no reason other than Apple says. After the High Sierra launch, I'm also getting worried my Adobe CS6 is going to be permanently broken by an upgrade sooner than later as well.
Basically, I'm not saying Apple is right or wrong here. Just that you're comparing Apples and Oranges when you talk about OS updates, and running an Android phone on the 2013 OS today is not remotely the same as running an iPhone on the 2013 version of iOS -- you couldn't even download modern apps if you were doing that.
