That is because you need to edit the item.dat so it doesn't (if you want it that way)

Number values:
Toggle object on/off
<unknown>
Color ID: REFER toribash.com/colors.txt
Alpha: 255 = fully opaque, 0 = fully transparent
Use texture overlay: body part texture is MULTIPLIED over the object color. If colorID is 0 or 1 or pure, the texture color is used as is
?Dynamic <unknown> currently shrinks/flattens object
Replace body part with object: 0 = body part is visible with object, 1 = bodypart is replaced with object
Ghost: 0 = object doesn't appear in ghost, 1 = object appears in ghost

You can see that the second to last number is the number that decides if you replace the part with object or not, so if you don't want that you want the second to last number to be a 0