According to the unofficial records, you could be correct. Andrew Johnson's maternal grandmother was claimed to be Mary Ruth Lindley, daughter of Captain James Lindley. Accordingly, Johnson's maternal grandfather was Ruth's spouse, Andrew McDonnough. The unofficial records indicated that she was also married to Colville Abercrombie, Sr.
And, for the official records, Captain Lindley was not a "traitor." He was a British Loyalist. It was the patriots who were considered "traitors of the crown" for the greater good.