Is Tethered enhancing the stereoscopic 'small model' effect somehow?

Tethered allows the player to scale the world up and down. When scaled down the strength of the stereoscopic effect and feeling of looking a tiny model seems to be enhanced beyond what I've been able to achieve by setting world to meters scale.

A couple of other games seem to have a stronger, almost tilt-shift-strength stereoscopic effect like this. I haven't been able to work out if it's been done by tweaking the engine or rendering options, or if it's a natural consequence of having a scene 'full' of artwork which just naturally leads to the effect being stronger.

Does anyone have any insight into this aspect of VR design with UE4?