In my opinion confirming the important point you made was that Kate and Gerry McCann co-operated fully with the Policia Judiciaria and answered all their questions at all times.
Over a marathon PJ interview lasting over eleven hours Kate answered every question put to her just prior to being made an arguida. She exercised her legal entitlement to silence having been 'read her rights'. What is wrong with that, pray?
It is worth bearing in mind that Kate and Gerry were made arguidos on the basis of the Amaral investigation's failure to fully comprehend forensic information.
Competent investigation of the facts of the case led by another coordinator, including a proper understanding of the forensic evidence meant that there was no evidence to charge anyone with anything. Which in my opinion proves that there was no evidence to justify making anyone an arguido in the first place.
This is a prejudicial situation recognised and addressed in the Portuguese Criminal Code by a change in the law which came into effect days after Kate and Gerry were made arguidos to ensure that evidence justifying the imposition had to be put before a magistrate.
In my opinion the arguido questions fade into insignificance when balanced against the imposition of arguido status in the face of a known impending change in the law under which it would most likely not have been allowed.
Witnesses are obliged by law to answer questions put to them. The connotations associated with 'co-operated' do not apply. They were obliged to do so.
Gerry, AFAIK, answered all the questions put to him. Kate did not.
The sequence of events is that Kate and Gerry made it clear they were going to leave Portugal. The PJ had a choice of interviewing them before they left or not. They chose to conduct the interviews. Based on what they had at that time, they were legally obliged to constitute K & G as arguidos.
None of this has anything to do with an impending legal change in Portugal.
Perhaps we can now return to an analysis of the arguido questions asked of Kate and Gerry McCann?