DCI Redwood announced on the same programme that he and his officers had taken the investigation 'back to zero' and were 'assuming nothing'.
Unless he is lying blatantly, that means just that; namely, that the McCann's must at some point during his investigation been considered possible suspects.
On that understanding, SY must hold information contradicting the notion that the McCanns are involved. Or, they must hold no positive evidence suggesting their involvement.
Totally agree SH. It's quite obvious that the first task undertaken by SY would be to thoroughly investigate the McCanns and their friends to the Nth degree - to see if there could be the slightest chance that Amaral's claims were credible - and also to establish whether the McCanns and the group were credible witnesses.
SY have far more information about the case and the people involved in it than we do - and also have the experience, the expertise and extensive investigatory powers that we don't have.
Pretending that we can possibly know as much about the case as they do is ridiculous. To go even further and claim that we know
better than they do is even more ridiculous imo.
Then there is that very large elephant in the room i.e. - Would the McCanns have constantly pressed for the case to be re-opened and re-investigated if they were guilty? Not a chance - as that makes no sense at all to any reasonable person imo.