I thought it was going to be about analyzing what’s eating up my phones storage (system storage I’m looking at you) - and note it focuses on Android only. Not sure how much of the analysis extrapolates to iOS apps.
A software dev colleague of mine bought a ZTE phone early in the iPhone era and the immediate thing we noticed is that it would peg the CPU, get hot, and run out the battery in a few minutes.
In the desktop world any program is entitled to peg the CPU as much as it likes; if it is blocking the render thread it might get some "tough love" from the OS, but otherwise it's not a problem. In mobile, the CPU is a precious resource.
Android has not caught up with the idea that anything is precious.
I don't know what your brand or last device with this problem was, but there's a reason https://dontkillmyapp.com/ exists. Most of the battery issues were solved years ago with Android 6 (and then the situation improved with 7 and 8).
An focused application (or applications, in split view) is able to drain the battery, but that's just intended behaviour. You wouldn't be able to use a battery app or play a mobile game like pokemon Go if the OS would limit the current application.
I've only experienced the overheating problem on some midrange to cheap (<€200) Android devices, but that's usually because of the cheap, inefficient SoC that's found in the bottom of the spec sheets.
My phone saves battery to the point of killing background apps that I don't want killed. Luckily, I can turn that shit off, though Xiaomi has three different ways to make sure background apps don't get killed that I need to work through.
I do really not want Google making this decision for me.
If they decide to display a warning, or create a new permission for that, fine. But it's really not something for Google to decide in a centralized, "we don't care about individual use cases" procedure.