The vast majority of a person’s genes – about 99.8% – are found on the 23 pairs of chromosomes that sit inside the nucleus in each cell in the body, and in the IVF procedure this DNA comes from the two parents.

However, a tiny proportion of genetic material also resides in a cell’s mitochondria, small structures that act as the cell’s batteries and float around freely in the cell body. In mitochondrial donation, the mother’s mitochondria are removed from her egg and replaced by a donor’s.

The treatment was originally developed as a treatment that could prevent women with debilitating or even fatal mitochondrial diseases from passing them on to their children.

The title seems a bit clickbait; imply a certain idea, and then its a single organelle that was transferred.

That's about as strong a case as saying "person found with 3 people's DNA" and it turns out they've had two organ transplants