I love when people argue about "true multitasking"
Unless you're ambidextrous and can have your eyes reading both sides of your split screen simultaneously, no one is ever truly multitasking, as in, performing two seperate tasks simultaneously. Even on a desktop with multiple monitors, you are never truly performing two independent tasks simultaneously with any sort of efficiency. Though having multiple monitors/multi window can certainly make some tasks more convenient and faster.
As for multitasking in the OS, meaning the OS allowing apps to run in the background... Yes, iPhones don't have the ram necessary to allow a bunch of apps to continuously run in the background. If you need a bunch of apps to run in the background, then iOS and the iPhone as they currently are, are not for you. The likely coming increase in ram could see this change, but who knows.