So, the more time the machine works on a project, the more that project costs....in tool heads and holding up the next copy being produced.
If you are a company that plans on painting it's product after machining, are you going to up the cost of production to get a smooth satin finish? No. You are going to finish it well enough that the coating doesn't belie the machine marks under it.
So, Busse runs them till they are in spec and smooth enough that there aren't marks coming through the coating, and then call it good. Why do more work on something that isn't meant to be seen?
It's not like they affect performance.
So, I honestly think it is just a matter of finer machining work is not necessary to achieving the stated product quality, and in fact, paint sticks to surfaces that are a bit roughed up better than super slick ones anyhow....