This feature does not work through masks because it uses a less secure method to scan only the area around your eyes.
Enabling this option notifies users that enabling Face ID with the mask makes the feature less secure than a full face scan, and they must look at the phone to unlock it without covering their eyes.
Apple has Apple decided that this feature will only work on the iPhone 12 and later models, which means that all iPhone X, Xs and XR users will effectively stay out of the cold.
Another important feature is in iPadOS 15.4, which is Universal Control. It allows the user to use the Mac and iPad in parallel and move the mouse pointer seamlessly between them. Users can also transfer files between two devices as if they were on the same computer.
In addition, 15.4 also includes several new features, including a new voice option for Siri and the ability to provide time and date information offline.
According to the GSM Arena, Apple also released watchOS 8.5, macOS Monterey 12.3, tvOS 15.4 and HomePod Software 15.4.
Source: The Nordic Page