Howdy guys - Yes you're right Bob, I'd say there'd be no actual connection with Harry Robertson.
Angus Robertson was at least a generation earlier, born in Broadford, on the Isle of Skye. Apart from fishing and seafaring he worked as the following:
"I've helped to biuld gold dredges, and worked on them after they were built. I worked in gravel pits and helped to make roads. I earned a living painting, gardening and splicing ropes. I wielded the hammer for a blacksmith. During another stunt, I broke 250 cords of firewood. I've been a minister of religion in this country [NZ] for years, and during that stunt I got a church built, and helped to build other institutions. I've been very successful at insuring life, for this world and for the life to come."
He also spoke and wrote poetry in Gaelic (and English) and could read Latin, Spanish and Italian too. Quite some fellow.