There are many 'Scots R1b' Highland families who have tested. They're into double figures testing positive for L21 last I heard. The Highland Clearances will explain why many are found in the Lowlands and the Colonies.
That must be the answer then, but in terms of the map, I cannot justify putting a placemark somewhere in the Highlands because an individual has what is thought to be a Highland surname and is somewhere within range of a modal haplotype.
I also don't put North Americans, Australians, and New Zealanders into one of the European categories or onto the R-L21* Map simply based on their surnames and/or the fact that they belong to a certain cluster characterized by a modal thought to have a certain geographic affinity. They must have a paper trail to the Old Country. That standard also excludes me from any of the European categories, which is why you will find my entry in the "Colonial" category and you won't find a placemark for my ancestor on the R-L21* Map.
I don't doubt that the Highlands are overwhelmingly R-L21*, but I guess getting some pins into the R-L21* Map there is not going to be easy.