Not the OS, the apps themselves do. A lot of them. On Android.

Exactly!

But now I see your point. You were talking about the OS implementation, not the user experience. From the user experience, it matters monkey's kidneys what an idle application does. Whether it stays idle in the RAM for as long as possible or is swapped out right away. As long as it does not impair the experience.

We have had a discussion on multitasking before. Even multitasking on Android specifically. It is all too well "ps -aux" showing you a bunch of stuff. By that reckoning, you can say that DOS was a multitasking OS too: it could play a tune while you moved the mouse cursor around the screen. But for me as a user, it is not a real multitasking if a video I am playing stops when I switch to the browser.

Multi = more than one. Task = task. Multitasking = doing more than one task simultaneously. I don't care that the OS can run many processes. If the OS stops me from doing more than one task, then as far as I am concerned, it does not support multitasking. Simples.