Oh wow, the color in the photo made it look like all but one were a dark brown to match the body, and one was black. As you said, probably a matter of how shiny. I've been known to put different color knobs on my basses so I can tell at a glance which knob does what, so I thought maybe you were doing the same.They are all black? And one is a Volume.
Oh, maybe you mean the lower right? I think that's just a lighting thing. And maybe that is the original Sadowsky knob so it's a little older. They are all the same color but that one might be a little less shiny.
I thought you might be asking why I wasn't able to justify ordering another one, despite my happiness with this one. No big secret, just that the wait would be an issue and while the communication was good when I had it, it was very sporadic.