Furthermore, the developers seem to have some issues with transparencies while converting, obvious to see at the Klyros "winglets" and Carkarass wings, and the Grendol body (non-transparent stomach). I would not be surprised if the converter cannot read a specific kind of transparency information from the original images, because remembering the "transparent waterfall" issue, it seems that PNG supports several techniques (palette index / alpha channel / own layer), but not all of them are supported by all tools.
DDS images can contain already pre-calculated mipmaps (lower resolution variants of the image for distant objects), and even normal maps (to apply bumpmapped detail effects). But because normal maps usually are based on a blue tone, I wonder if Grendols have a normal map which was added like a normal texture, not like a bumpmap effect. Because they were never so blue before.