In the latest version of Rhino 8 (8.1.23325.13002, 2023-11-21) for macOS, imported and then horizontally mirrored Picture’s (i.e. JPG) in the XY-plane seem to switch to their original, unmirrored transform, when panning the viewport, and back when releasing the relevant mouse button.
If my SystemInfo is of interest, you can find it here.
Also while zooming in and out, entering and exiting command, etc.
RH-79202 is currently on the list of things to be fixed in Rhino 8 at some point. The list of bugs and requests is mostly open, and you can check the status of an individual item by following its link.