Yes, but normally 4- or 8-wide is the norm: the wider you go the more sorting you have to do to traverse things in order or find the nearest hit which has an overhead (hardware may help with this, but it's still an overhead).

Previous indications from Nvidia about their BVHs don't seem to show anything about very shallow trees for any of the BVH algorithms that OptiX supports (scroll to bottom for reverse visualisation of a BVH hierarchy on top of the Stanford Bunny model): https://drive.google.com/file/d/1B5fNRFwv2LsGlCBJ8oKYRiiDUtL...