I'd argue that it's even starker and simpler.
IMO, if the ECHR conclude that there's sufficient evidence to show that prior to Knox's first verbal "confession/accusation" in that 5th/6th Nov interrogation, the police were accusing Knox of having lied to them up to that point about her movements on the night of the murder, and that the police were telling Knox they had evidence that in fact (and contrary to her accounts to them up to that point) she'd met with "the killer" and taken him to the cottage, then the ECHR must conclude that by definition the police were considering Knox as a criminal suspect before she ever opened her mouth to accuse Lumumba. Whether the police suspected Knox of lying to them to protect the killer or they suspected Knox of personal direct involvement in the murder is immaterial. Both of those things are serious criminal offences.
And IMO there's sufficient evidence to allow the ECHR to conclude all of the above. The main pieces of evidence are 1) Knox's continued and unwavering insistence, from the night of the interrogation onwards, that prior to her first "confession/accusation" the police were accusing her of lying and that the police had evidence that she'd left Sollecito's apartment and met up with the killer to go to the girls' cottage; 2) the court testimony of police "interpreter" Donnino, who clearly stated that she'd used a personal example to suggest to Knox that she (Knox) might have suffered traumatic amnesia; 3) the words of Perugia Police Chief de Felice, who told journalists that Knox had "buckled" and "told the police what they (the police) knew to be correct".
So I think it should be straightforward for the ECHR to find that Knox was definitely being considered a criminal suspect well before she ever made her first verbal "confession/accusation" - the infamous "He did it! Patrick! He's bad!" outburst, and that this outburst was directly made in response to something that more-or-less amounted to a police instruction to say that she'd met with Lumumba and taken him to the girls' cottage where he'd attacked and killed Kercher.
But....... even in the (extremely unlikely IMO) event that the ECHR concludes that there's insufficiently strong evidence to allow for such a conclusion, it will then consider what happened (and didn't happened) once Knox made that first "confession/accusation". The indisputable fact that the police went away and typed up a statement for Knox to sign, all without informing her of her rights, is a slam-dunk indicator that Knox was denied her proper rights.