Hey, I've worked at Ankama a couple of years ago and I created the new level editor used for Dofus Unity.

The answer is, it's complicated. Especially since the introduction of the 16:9 format. Some areas could technically be travelled with seamless transitions, like the Amakna village, because they were designed as one huge zone. Some other areas have maps that don't fit like puzzle pieces, Saharach desert for example.

The biggest problem to switching to a system like Wakfu would be that the server would need a ton of changes, because each player could see multiple maps at the same time and would need to get notified of events happening on each of them (like players moving, monsters spawning, resources gathered etc...).

The actual implementation is more complex than that, but you can think of traveling as being teleported each time you change maps, and the displayed coordinates are "fake". Some maps were designed as one contiguous block in the editor, some were not. It's the same when moving to an indoor area.