I only have single-boot, so I've not hit this problem.
But I note that Planet have shifted the way they describe it, so that it now makes more sense. (IIRC, they now say: press Esc until you feel it vibrate, then wait until the first splash screen (with Tux), then hold the key(s) for what you want to boot.) That seems fairly clear to me.
A boot menu would be clear, too, of course — especially for folk who booted into other OSs rarely enough not to remember the different keypresses.
I guess the downside there would be for folk who are frequently switching between two OSs, as they'd have to wait for the menu each time instead of going straight to the other OS.