You are absolutely correct Jack. I made a mistake in my classification of these names (old age and overwork!) a while ago.

We have seen a number of similar examples emerging from the Manx Y-DNA study where male lines descended from one common ancestor have ended up today with different family names.

The phenomenon that must have occurred is that individual men had sons, who themselves reproduced to create separate lines of new generations of male descendants. These descendant family lines lived separately from each other, but at that period of time when the old Gaelic patronymic family names (which of course changed every generation) started to become hereditary and constant from one generation to the next, each family adopted a different name from each other, depending at the time on their father’s name, where they lived, the occupation or appearance of the father etc. So genetically all these men were related, but they adopted different family names for their descendants. In hindsight this can be seen as an inevitable consequence of a changeover from a patronymic naming system to a hereditary one.
cheers