Yeah, it will auto-apply certain LUTs on clips to bring it to Rec 709 at import depending on what it detects. It's meant to do that so you can quickly preview footage in a linear color space, and I suppose it doesn't move it to wide gamut because people are unlikely to be able to preview it on a wide gamut display... either that or they just overlooked it. Personally, I think it's an annoying feature, but it takes a few seconds to change it so I don't care too much. There should be a checkbox in the import window or in preferences to turn this off, though.
The Inferno as far as I know can display HDR, so that's why you'd be seeing it properly. On the iMac Pro you'll be getting the tone mapping which is throwing away tons of data to push it into a standard dynamic range. Remember that the iMac Pro display has expanded color, but it's not HDR. I mean, it could be a bug with how the tone mapping is happening, too, so it's hard for me to say without seeing it all.