scrot versus maim, capture whole X screen of two monitors

I am using linux Mint 20.3 MATE, with two 1920x1080 physical displays, one landscape, the other portrait. Accordingly, X11 has set up a 3000x1920 'screen', with the two displays mapped to it, like this. I am able to seamlessly move the mouse and non-maximised windows from one to the other. I can also move and expand windows to overlap into the non-display parts of the screen. Scrot and maim behave differently. Scrot captures the whole screen, including the non-display areas, which X11 has actually rendered correctly. I find this feature of scrot useful, as I can drag and expand a non-maximised window to almost the entire 3000x1920 screen, and capture the whole of it with scrot. Maim is 'intelligent' and only captures the areas that map to the physical displays, recording the non-display parts as black. Unfortunately scrot's -s selection option doesn't play nicely with many webpages, while maim's use of slop seems to be solid. Can maim be persuaded to record the non-display parts of the screen that X11 has already rendered correctly? The -g option, which defines the pixel coordinates I want to capture, as wxh+x_offset+y-offset, runs without error, but still ignores the non-display part. I'm not sure I understand the syntax of other capture options from its man page. I am concerned that scrot might be 'improved' in the future, to copy maim's behaviour.