No mistake... Its a figure of speech.
I'm suprised it took so long for some of the know-it-alls here to point out that there isn't a "dark side of the moon"... Unless we are talking radio astronomy...But then I wouldn't expect them to think beyond visible wave lengths, or that even in terms of visible light, nearly every square centimeter of the moon's surface is "on the dark side" for 15 days each month.