Having looked at the instructions for each page, they are somewhat different. The 'Seat Navi System' instructions mention MapCare and how you shouldn't follow the process unless you have it and the Plus system instructions don't mention MapCare at all.
So it seems the later 'High' systems on MY16 cars do not require MapCare and the update can be done yourself, whereas the earlier pre-MY16 requires MapCare.
Not sure where you stand if you have a pre-MY16 with High though....
He talks about a charge for the "card" so it can't be the nav high because the nav high keeps the maps on the hard drive.