Praise be to Allah.
This is not true, and I do not think that any half-human, half-jinn person could be born, because the jinn do not have bodies. They are spirits, even though they may appear in different forms. These people who are known for their tracking skills are people who are possess powers of observation, intelligence, knowledge, experience and skill. Allaah has created differences in tracks and footprints, just has He has created differences between people who may be tall or short, white or black, small or big – so that among one hundred thousand people you will not find two who are the same in all respects. This is the reason why these people can distinguish between things, and they recognize tracks and can tell apart things that look similar. And Allaah knows best.