It’s got:

• Horizontal rulers at the top of the frame showing where (1) page actions, (2) page title, and (3) the search bar (if applicable) go
• Horizontal rulers at the bottom of the page showing where the tab bar goes
• Vertical rulers at (1) the standard iOS side margins and (2) the centerline
• A single-layer status bar – easy to delete or change to white, as needed
• A single layer device outline (including notch)

And it makes it dead simple to lay out apps in a “typical” iOS style.