The sources I see online are contradictory. Some claim that the only source of cholesterol is from animal or dairy products. However, others suggest that cholesterol can also come from trans fatty acids, e.g.:
https://www.livekindly.co/how-do-vegans-get-cholesterol/
"LDL cholesterol is found in trans fats, which is found in processed foods and naturally in meat and dairy. The Mayo Clinic notes that this trans fats are “double trouble” for heart health due to the fact that it raises LDL levels while lowering “good” HDL levels.
Trans fat is added to processed foods through an industrial process where hydrogen is added to vegetable oil, which allows the oil to be solid at room temperature. On ingredients labels, it’s called “partially hydrogenated vegetable oil,” and it is used to give many packaged foods a longer shelf life."
Perhaps the only 'natural' source of cholesterol in unprocessed food is animal and dairy, but it can be created through heavy processing, like in trans fats.
All that said, 1mg sounds like it could be an error or rounding choice.