While iOS for iPhone and iPadOS for iPad are closely related, some features and Apps are unique to one or other platform.
Unlocking iPhone with FaceID, while wearing a mask, was only introduced in the most recent update to iOS 15.4. Contributors here have absolutely no insight into Apple’s product development or release programmes - and can offer no information at all concerning potential future release of this feature for iPadOS.
Apple do, however, invite submission of comments and feature requests via their Product Feedback portal. For iPad and iPadOS:
Feedback - iPad - Apple