I'll get you a picture, it is a very different piece/solution than the picture you lightened from the Design Studio. It is a solid 1x2 covered in the interior material, permanently attached in the car but not attached to the seat in anyway. It supports the second cover. Again, I will get you pictures Sunday.Personally I am convinced Tesla planned the additional part all along.
The signs were clear in all the shipping 5 seaters as well as in the Design Studio almost from the start:
Speculation: Model X five seater is missing a panel to hide seat bottoms?