Most of Anima Mundi is made with stock footage, coming probably from Tv documentaries. Thus, the orignal format of these shots is 4/3, being composed with in mind the tv sets of those times.
The fullframe version was released, I'd just like to have a look at it. Having read this thread full of love for Mr Reggio's work, it wouldn't be surprising a laserdisc rip made its way to the internet.