Accessory makers Dbrand have taken their Steam Machine Companion Cube case off sale, admitting they never actually sought permission from Valve to make it.
The issue isn’t making a 3rd-party case for Valve’s hardware, it’s making that case resemble an object whose image was created by and is owned by Valve. the fact that Valve both makes the hardware and owns the image is coincidental
you can make an iPhone case without any issues from Apple, but you can’t make an iPhone case with images of Disney characters on it without permission from Disney
The issue isn’t making a 3rd-party case for Valve’s hardware, it’s making that case resemble an object whose image was created by and is owned by Valve. the fact that Valve both makes the hardware and owns the image is coincidental
you can make an iPhone case without any issues from Apple, but you can’t make an iPhone case with images of Disney characters on it without permission from Disney