I'm not sure, Icabodcrane, it would have been easier, when they concocted the third time-line, for Matthew to be uncertain about the state of the curtains.
The lack of forensic evidence that someone passed through the window made their dramatic "jemmy" description (the crucial ingredient in the story telling) collapse and they needed a second best : the whooshing curtains revealing a horrible dark opening on evil.
ah, but that would be making the assumption that Oldfield was involved in the 'concoction'
What if he was innocently speaking the truth about what occured that night, ? ... there might be a need, then, mightn't there, to 'incorporate' his recollections into the 'Jane saw the abductor making off with Madeleine at 9.15 ' story
So instead of sticking with the first statement, where the open curtains/ window/ shutters were the
first thing Kate noticed (
before she even realised Madeleien was missing ) Kate changes her mind, and says she already knew Madeleine was not in her bed before she noticed the open window ... only brought to her attention when the ( closed ) curtains '
whooshed' up following a timely gust of wind
For it to have been possible for Jane Tanner to have 'seen' the abductor at 9.15pm ( as we have reletlessly been told by the McCanns she SHE
DID ) then the room would have been exactly as he ( the abductor ) had left it at 9.15pm
That's how Matthew Oldfield would have found it at 9.30pm ... and how Kate McCann would have found it at 10pm
There would have been been no change in the situation in the room between those two checks ( presuming, as the McCanns insisted, that Madeleine had been abducted just after Gerry's 9.10pm check ... as witnessed by Jane Tanner )
And yet there was
Matthew Oldfied said the curtains were closed when he checked at 9.30pm ... and Kate said the curtains were open when she checked at 10pm ( an anomaly that could only be explained by any abductor having struck between 9.30pm and 10pm .... nixing Tannerman )
The anomaly was 'fixed' when the story changed
Oldfield did not change his story ... Kate changed hers