There's a different between "fine" and "luxury". You don't want to cross it, that's your prerogative. You can judge others, that's also your prerogative. But that doesn't make you objectively correct. The iPhone will obviously work better than your PoS chinese phone. You pay a premium for that. Don't hate on it if you can't afford it or don't want to afford it.
Oh my god. Can you at least do your research now ? They wrote the core bits and not just userspace utils. Did you read what they wrote before blustering here ?
If you didn't know you should have clarified before making such sweeping statements. Who knew writing an OS would count as systems programming experience.
A good way to think of this is a git checkout from anywhere . And then all future commits happen in a branch / detached head state, not affecting the place you checked out from i.e. original timeline.
I worked on a smart watch team. Turns out writing a simple while loop and a simple task model, cooperative scheduling, let us sleep our processor more often. It was also very light weight in terms of memory. Basically not having the burden of traditional heavy weight OSes really helped get good battery life.