As for the blank part in Argentina, note following disclaimer on the Garmin website:

External country boundaries and other data as depicted in the map(s) may be neither correct nor authentic. If a country disputes the location or accuracy of certain features in our data, we may remove the disputed data from the product until the dispute is resolved. There may be voids in this product for this reason.
So maybe the UK does not only claim the Falkland Islands, but (part of) the main land of Argentina too...