App switching on iPad iOS 12 doesn't make sense...
Four finger swipe switches between open apps, in a linear fashion, just like you would expect. Imagine having a row of open apps and just sliding between them (similar to virtual desktops on macOS).
BUT that only works until you interact with an app. Do anything, just a single touch inside an app, and BOOM, the row is lost, this app becomes the last one in the row regardless of its previous position.
If you had some app on the left, it's no longer there. This is extremely confusing and doesn't make sense to me. The only useful use-case here is that you can switch between two apps quickly this way, BUT only if you interact with each app after switching.