I chose my words poorly when describing the oil color. The oil out of my '04 was dark, but translucent. The oil out of my '21 is black and dirty. Wipe some on your fingers and you have to scrub them with a brush to get them clean. The '04 oil just wiped off with a shop towel. It did not stain your skin. Hard to explain without pictures, but there is a definite difference.
Exhaust brakes are new to me and I did make use of mine quite a lot on my trip through Idaho and western Wyoming. Do those have an effect on oil contamination or is it the emissions controls, namely EGR, that dirty the oil?
The drain plug I purchased to replace the one in the picture has a completely different surface finish. Very smooth, compared to the rough and grainy finish of the flawed plug. The original one looks cast, which I'm sure it is not. I think it was just a bad part that slipped through quality control.