Relax – you've just misunderstood. As the comment above points out, this functionality is affected by a specific setting on a Mac – there's a toggle labelled "

Relax – you've just misunderstood. As the comment above points out, this functionality is affected by a specific setting on a Mac – there's a toggle labelled "Displays have separate Spaces", which is checked by default. When it's checked, each display has its own independent set of virtual desktops and fullscreen apps, which can be navigated independently of the others. When it's not checked, there is one shared set of virtual desktops that span all displays, and navigation affects them all. When using the former option, windows are restricted to appearing on a single display only – they cannot span multiple displays. This is a reasonable choice, as it would be otherwise unclear what the interaction between windows, desktops, and displays would be. Each display is its own independent canvas and interaction is limited to migrating windows and apps between them. If you are using the latter option, then windows can be stretched arbitrarily across multiple displays. This doesn't present a problem, because the extended display then represents one common canvas and it's clear how interaction between the windows, desktops and displays should work. See? It's no magic, or broken, or the outcome of buffoonery. It's just a normal computer feature working normally.