What is the difference between the circles?
A company is in charge of running/moderating a manufacturer circle, whereas owners are responsible for running an owner circle. Usually the owner circles are for groups that want to discuss a company's products, but the company will not/can not participate enough to run it themselves. In the case of Norh, the company used to participate and then dropped off, so owners volunteered to moderate and the circle was moved to the owners section (if owners weren't willing to moderate, the circle would have been removed entirely).
In the case of Salk, the company is actively participating, so it makes sense for them to take the responsibility for moderation and move into the manufacturer section.
In short, there's an expectation of manufacturer responsibility and participation in the manufacturer section, but not in the owner section.