A WH is a tunnel entity : They have a source structure and a destination structure. When the entity is despawned, so are its source and end structures ; THEN the source is respawned, within the limit of its available systems.
Wandering WH have a source that is not limited to one system ; static WH have.
The structure of the destination only appears when someone warps to the structure of the source the first time. (or after a delay) => closing the static.