If they have information that was only present on your device or your iCloud backup, and they already can't get at your device, how exactly does parallel construction help them explain the fact that their evidence includes information that could have only been obtained one way?
Because that's not the evidence they present, they use that to figure out where else to look for evidence, pretending they found that randomly or by guesswork or suspicion or following an anonymous call.
Right. "By virtue of my training and experience, I had reason to believe" is a stock statement re anything, in trying to establish probable cause for searches, stops and the like.
It's a broad, overarching, and highly vague statement that amounts to, in many cases, "I decided you do, so therefore I have the right to act as if you do".