I think they were a little off in their understanding. It uses material from 3 people but the material from the egg cell donor is not the genetic nucleus, it's the rest of the cell's contents. The mitochondria (the power-source of the cell) remains in the egg cell body and does contain mitochondrial DNA from the cell body donor, but it's the contents of the nucleus that contain the chromasomes which determine everything else about the offspring. So it's a body and batteries, essentially. Those batteries contain scraps of code form the 3rd donor but it's like switching Duracell for Eveready. Different name, slightly different formulation, but makes no difference to the appearance or function of the finished product.
Re: John/Sherlock/Mary
The mitochondria (the power-source of the cell) remains in the egg cell body and does contain mitochondrial DNA from the cell body donor, but it's the contents of the nucleus that contain the chromasomes which determine everything else about the offspring. So it's a body and batteries, essentially. Those batteries contain scraps of code form the 3rd donor but it's like switching Duracell for Eveready. Different name, slightly different formulation, but makes no difference to the appearance or function of the finished product.