She did give specifics of action. She said Patrick wanted to have sex with MK, that she covered her ears while he was raping her. That seems like more detail than the police needed if all they wanted was for her to place herself at the crime scene or accuse Patrick.
Wearing that t-shirt at the trial indicates she wasn't scared of Italian justice. This was after them supposed hitting her in the head and using mental mindgames to get her to say what they wanted. You'd think she'd show up in her most professional looking attire.
So, you expect a non-professional to a) have professional looking attire, and b) still have it after going to prison, and c) know enough to wear it to court. That's not a supportable assertion by any means.
No, she did not give specifics of action. She did not say when she met Lumumba, what part of the square/steps she met him at, what he was wearing, whether Sollecito was there or not, wheter Meredith was home or not, when why and how Lumumba went into the room, whether Meredith had interacted with Lumumba first or not, or indeed, any other detail that would actually reliably place her at the scene. You know, the very thing the police are questioning her about. It's not just about getting a name, but getting usable information to use against that name later.
The police need more than a mere "Patrick did it" if they want to arrest him with any chance of actually proceeding onto a charge. Can you imagine if the defence for Lumumba had cross examined Knox in court and found she couldn't provide any details? She, and thusly the prosecutions case, would have been slaughtered.
Her 'confession' is full of 'I can't remember' and 'I think' and other general vagueness. Had Lumumba been found guilty, you'd undoubtedly be pointing to her confession as a masterclass in being intentionally vague.