What's to agree on? You either have multiple, concurrent tasks or you do not.
You clearly have the ability to receive phonecalls at all times, so the phone is running so you have multiple concurrent tasks so there's no argument.
Except there is an argument, so that isn't what's really being discussed even if the discussion is framed by that term.
Edit: Whoops. I'll leave the comment but I do realize this isn't an iPad thread.