Looks like ripples behind the boat would be reasonably expected. I am not sure we have enough resolution to see effects of small ripples in the relatively featureless area behind the boat. I would not expect ripples from a rowboat to have any effect on the reflection of an island in the distance, and somewhat ahead of the boat. If we had pictures of the "rowboat" after it passed the "island," that would tell us more, maybe. But we do not.Surely man in a rowboat means ripples on the loch which means a glassy still lake surface perfectly reflecting sky is an impossibility?
I am not arguing for the rowboat hypothesis, I'm just not sure the absence of visible ripple effects says much one way or another.