On a 16" M5 MBP running 26.7.2 I have the display set to "1496 x 967" in the display section of Settings.app; the native resolution of the LCD panel is 3456 wide per the "System Information" report. When I inspect DOM nodes in a full screen width browser window, nodes which span the width of the screen show the expected 1496 CSS pixel width.
However, when I run a Mac Catalyst app in Xcode, with its window at full screen width, and I inspect the bounds property of a UIView with the full width of the window, it reports its width as 1943 points wide, which doesn't match the value I expect (1496, same as FF sees) or the 'native point-resolution' of the display at 2x (1728 points). Furthermore, the nativeScale property of the UIWindow is 2, which combined with the point width contradicts the actual resolution of the LCD (i.e. 2*1943 != 3456.)
I've looked for documentation but haven't found any. Where is 1943 point width coming from and why is the nativeScale 2? I was expecting 1496 and 1496/3456.