With the update to iOS version 18.0, there was a significant improvement in information security and user privacy, allowing apps to be locked using FaceID (or TouchID), with no possibility of using the phone's unlock passcode to access the locked app (see reference: https://www.reddit.com/r/Wealthsimple/comments/1fr1nnj/psa_ios_18_require_face_id_feature_mitigates/).
As a result, even if someone else knew your iPhone unlock passcode, they wouldn't be able to open the locked apps, as FaceID (or TouchID) would be required. However, after updating to iOS 18.1.1, someone who knows your iPhone unlock passcode and is using your iPhone (or has stolen your iPhone and requested the unlock passcode) can inadvertently open the locked apps, because after a few failed attempts to open the locked app without FaceID (or TouchID), the iPhone will prompt for the unlock passcode to open the locked app.
Even if the user has moved the app to the hidden folder, the content of that folder and the hidden apps within it can be opened with the iPhone unlock passcode after several failed attempts to open the hidden app without FaceID (or TouchID).
It would be very important for users if this security and privacy weakness were eliminated, returning to what iOS 18.0 did: the only way to open a locked app is through FaceID (or TouchID), and it would not be possible to open it with the iPhone unlock passcode.