I think this setting should be flipped by default, so that workspaces affect all monitors, at least in the mode where the 2nd (3rd, etc.) monitor extends your m

I think this setting should be flipped by default, so that workspaces affect all monitors, at least in the mode where the 2nd (3rd, etc.) monitor extends your main desktop. In 2-screen presentation mode, it makes sense that the 2nd screen doesn't change when you change workspace, because you're presenting something there.