They don't were exactly the same cops but that's not important, because what matters is that Knox did not complain nor reported of any abuse, nor her lawyers did. Moreover, her own testimony and that of witnesses are against her; she has no credibility. And, what also matters, is that in any event her hand written note and statements are not explained nor justified by any alleged police wrongdoing.
Is she lying? Yes, yes she is lying, because she did not report the alleged violation to anyone before. The rules of the game are that a person who suffers an abuse needs to report it, at least to lawyers; attorneys have a duty to ask, and if attorneys obtain information about it, they have an absolutely compelling duty to file a formal complaint. Not only that; but Knox also received visits from parliamentaries, such as Catia Polidori (the laws provides a right of legislators to access prison falcilities for the explicit purpose of interviewing people in custody about possible abuses and about their treatment).
You say you would think "whatever the law says" (!) the cops would want to record everything to protect themselves from such beastly allegations.
Actually the only thing I agree to, is the word "beastly". These allegations are in fact good for non-Italian listeners who apparently don't know anything about the context nor about the law, and who have an already twisted mindset which allows them to obliviate the actual gravity of Knox's and Sollecito's set of statements, including those that were obviously non-coerced.