As we now know and suspected before , the review and investigation were never open.
The Mccanns were not investigated.
The question is why, as they remain, no matter all the bluster in any other direction, the two people who last saw their daughter alive.
You forgot to put 'In Your Opinion'.
As you keep pointing out - the 'crime is unknown' - therefore it follows that abduction is a possibility - and if that is the case the McCanns are not the last people who saw Madeleine alive.
According to SY all of the evidence that came into their possession was studied. 'All of the evidence' would include any evidence pointing to the McCanns - if it existed.
As the following quote clearly shows - the idea that any evidence they had in front of them would have been ignored is ridiculous. (bizarre).
Quote
Q: The first detective in charge of the case said he was going right back to the start of the case and accepting nothing. It seems very much he was suggesting that it was going to be a brand new investigation.
MR: It’s a brand new investigation, you are going in with an open mind.
You are not ignoring the evidence in front of you. That would be a bizarre conclusion. You would look at that material, what does it prove, what it doesn’t. What hypothesis does it open what does it close down and you work your way through the case.
End quote
As SY have said the McCanns are not suspects then it follows that they found no evidence to implicate them during their thorough investigations.
SY are the professionals and have a great deal more information and expertise than anyone else. It's ludicrous IMO to suggest that armchair detectives with only partial information and no professional expertise know better than they do.
AIMHO