The Norwegian page is slightly more helpful. It says that onboard announcements will be given on flights where passengers with checked luggage should use Connecting Norway. It certainly was announced on my ARN-OSL flight on Friday.
As I said, I had a LH-issued boarding pass and a 117 ticket. If the assumption is correct, that it has to be a 117 document, what would happen to passengers with luggage and a 701-document (WF), or for that matter a LH ticket which I certainly may have had on my SK-LH-LH-SK-SK itinerary. If a SK document is required, a passenger might be separated from his luggage, which from a customs perspective wouldn't be very sensible.