You need to learn the difference between a lie and a misinterpretation. In the phenomenon known as Chinese Whispers is each person recounting the information slightly differently lying?
Of course they're not lying - that's why they are called Chinese whispers.
Chinese whispers are not lies - they are misinterpretations/misunderstandings. Also they are far more likely to occur as a result of conversations over the phone - because when people are talking face to face they can correct anything the other person may have obviously misunderstood or misinterpreted as they go along. Not so once you have put the phone down and the other person is then phoning others - and so increasing the chances that even more chinese whispers can accrue. For instance 'Gerry said the door was open' (meaning the bedroom door) becomes 'Gerry said the front door was open'.
It's clear that the McCanns never told the PJ that that the shutters were broken or smashed - otherwise Amaral would have mentioned it in his book and surely it would have been one of the 48 questions?
And anyway - what would be the purpose of having a 'cunning' plan to lie to their friends and family? What did they have to gain? All that would do is prove to the PJ what massive liars they were once it was discovered that the shutters were undamaged. So the answer is 'Zilch'. They would have to be verging on the simple-minded to think that lying about the shutters was a good idea.
Unless people are so desperate to believe the McCanns lied they are prepared to throw all semblance of common sense and logic out of the window - then to claim the McCanns OR their friends and family deliberately lied about the shutters is plainly ludicrous IMO.