Tested in 14.0 - and 14.0.1... - Macbook Pro M1 Max, 64gb RAM, OS Sonoma 14.6.1
When using a second display (in Loupe Normal, FULL SCREEN mode), making any edits such as those in the basic panel for example, or local brush adjustments, mask adjustments etc aren't reflected in the secondary display - the edits just aren't applied to the image on the second screen.
Moving to another image and back will update the secondary display and show the edits, or if you remain on the image - enabling the crop tool and making a slight change to the crop area will also force the second display to update with the edits - otherwise the image shown on the second display remains unchanged (although the changes are applied to the actual image).
Note: Only applies when secondary display is in full screen mode. If you disable full screen mode so the secondary display is in a window, then the edits are reflected live.