From what I understand there is a continuous line of MALE descent to the Duke of Somerset, but male dna is harder to extract, and if there was no match, one might assume there was an illegitimate birth along the way. (obviously not from R III, who had no living descendants)
I am not aware of whether this test has been undertaken as well as the mtDNA. (in the TV program, it was revealed they also had a lock of hair from one of the plantanganets, but they were unable to extract the dna from it)
The original genealogy to trace Joy Ibsen was done in 2004, and took about 2 years, and was not undertaken with this recent dig in mind.
Since the discovery of the skeleton, Leicester University have traced another person for the mt DNA, and well as Joy Ibsen's son, Michael Ibsen.
To be honest, I really thought they were going to say it was inconclusive, so I was delighted to hear the dna tests gave a positive result.
Regards