We are seeing the same problem that William Temple had this summer, where OSTree refuses to store an image with devices on it. We understand that devices should not be in image, but sadly Ubuntu image has them and therefore thousands of other images do as well.
If we block the creation of the devices when exploding a OCI Image Bundle, we end up with something that is different then what is downloaded and this could potentially cause problems with mtree checking of the image on disk versus the image as shipped. Is there a reason OSTree does not work with Device Inodes?