I don't think they designed it that way Steve, they just didn't flip the polarity in that drawing. Which is a sin, but not an unknown one unfortunately. I've made the same mistake myself when drawing up a final circuit diagram late at night in a different piece of software to the design package and missed the glaringly obvious. Let's be honest: those two circuit diagrams have been there since the 1st post, and neither of us noticed. 
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