We are in a really weird situation where we agreed not to lock phones but I have plenty of reason to want to dig through hers.
Think back to your wedding day...You agreed to many things, including fidelity to one another. You probably swore before friends and family that there would be no one else and we see how much she has honored that commitment. There isn't a person alive who would try to argue that your commitment to fidelity is on the same level as your commitment to not look at each other's phones. It is like comparing a paper cut to being disemboweled, they just aren't on the same level.
I see you have several posts on the board this week and it is quite clear that you are struggling, which is to be expected. Again, back to your wedding day, you didn't ever plan to have to be marriage police. You asked about ethical boundary crossing as if there was an ethical boundary for your WW to go off fucking another dude...again...you wouldn't even be in the position to have to peruse through her phone if she hadn't cheated on you. If you have done any reading around SI, you will find that cheaters follow what we jokingly refer to as "The Cheater's Handbook" and your wife seems to have purchased a copy and read it cover to cover multiple times because she is following the playbook.
Cheaters lie and then lie some more. They know what they are doing is ethically far more egregious than any snooping through a phone. Those who have nothing to hide don't hide anything. Take me for example, I am what we refer to here as a Madhatter, which means that my wife and I were both unfaithful to our marriage and in our case, it was for a duration, simultaneous. When I was in the midst of my emotional affair, it was rare that I ever let my phone out of my sight for very long and since my wife is the one who has paid our bills for most of our marriage, there were times that I needed to hand her my device to get a sign in code and whatnot, I would be an anxious mess, just hoping and praying that my AP wouldn't choose that specific moment to reach out. I've been no contact with my AP since December 2019, so about 4 years and change, fast forward to today, my wife had my phone for hours just the other day when she was paying some bills and in that time I went to the store to pick up a couple of items we needed for dinner, went outside with our son and shot hoops with him and his friend, came inside, took a shower and actually had to use my Apple Watch to find my phone only for her to tell me that she left it in the office charging when she had finished hours before. I have nothing to hide on my phone and it is the way to live one's life.
All of that is to say that your wife hiding her phone is the issue. If you have nothing to hide from her and are not being unfaithful, don't lose any sleep over her looking at your phone. There is a saying, "The hardest thing to escape is your own perspective" so I acknowledge that, but the thing I have to ask in 2024 is, why are your phones not locked? My iPhone is the key to my home, a key to my car, my wallet, my camera not to mention all the personal, private information that I have stored on the device in various forms such as pictures, emails, passwords, banking apps (and their passwords), etc. At the very least, you should have a passcode or touch/face ID enabled for both you and your wife to safely and securely access those sorts of things. Now, if you don't use your phones for all those different things, that is a bit different story, but not having some sort of lock on your phone is a practice I would urge you to reconsider if for nothing else than to protect your private information from being exposed.