The material looks good, IMO (until I see it in more detail) - at least a good start. However, they need to cut the fabric on a diagonal to make the ribs of the weave sit diagonally as well. They might actually be straight on their fabric if it's not actually a twill weave.
The costumes were made out of a throw with a thick twill weave, which is one of the most common fabric weaves around, and everyone has examples in their home or on their person (denim for example is twill). The most difficult thing at 1/6 scale is to find the right rib count per inch, a good thread diameter and a suitable weight (thickness).
I hope the Sideshow stuff doesn't have any stretch to it, that would be bad for futzing and water treatment, IMO - it would also be problematic for fraying the edges. I've got some ideal material here that was from a painter's fabric tarp, though recently have also seen some table cloths that would fit the bill well (both require dying to the correct color).
The heads on the actors in the movie were just covered in fabric and what appears like gaffer's tape - it was just supposed to black out the entire contents of the hood except for the eyes. I wouldn't expect Sideshow to copy the prop details and I'm sure if they used some type of fur there would be some people pissed off. If the head is smooth, that's fine with me - makes it easy to stick or glue things onto later.