Yes, as cmroanirgo notes, they're renowned for this, and sometimes it can be quite amazing to 'spot the poo' after you've left some object out for only a day or

Yes, as cmroanirgo notes, they're renowned for this, and sometimes it can be quite amazing to 'spot the poo' after you've left some object out for only a day or two. I see them regularly on 50mm wide poly (irrigation) pipe - the accuracy of placement is astounding. Wombats are territorial, and very regular in their nightly movements. The cubic poo may be in part a simple consequence of their body shape (squat, narrow, long - evolved to wiggle into tight holes leaving only their impenetrable back plate exposed to would-be predators through the day), or, as you observe, assisting in perching scat with less risk of it being moved. As I understand it, the extra height allows for other animals to more easily detect (by smell, I'm guessing, but may be visual as well) their presence in the area - presumably with the intent that those other animals keep away.