You actually pulled that straight out of the air! If the OS took 10MB, your telling me you'd need 4G to multitask.... Man, those old Unix Linux and SCO machines running X must have multi-tasked real bad then with 64MB of memory in the early 90s. Even though I ran servers on them receiving thousands of Audiotex calls per hour; up to 24 at the same time.
And yes, these little programs were multi-threaded back then...
There is no such general principles and you know it, so where do those "rumors" come from exactly?
That Android needs 2G to barely function has nothing to do with IOS. BTW, Safari still reloads on the Air 2 with 2G even when there is memory left; the reloads have more to do with how Safari work than memory.