With regards to the Late Late show, well I thought it was good marketing that's for sure. The feature they showed (Genetic Communities) is currently in Beta and hasn't been rolled out let.
In case of Healy-Rae it actually make sense given that up until 1606 there existed a seperate county in West Cork/South Kerry eg. "County of Desmond" which basically reflected the Kingdom of Desmond which has resisted Cambro-Norman incursion under the rule of the McCarthy's
If you look at that map ye'll see that the "O'Healy" are down as landholders to east of Muskerry, in what is now County Cork, but which wasn't part of Cork before 1606.
It made for a great laugh, but we have to remember of course is that our concept of counties is very much a social construct that develop out of conquest, many of course do have some basis in previous overkingdoms but the boundaries are often fluid -- for example Western Offaly was historically part of Meath (Westmeath actually reflects better sub-kingdom of Midhe, whereas (East)Meath represents Brega -- within the province of Midhe), likewise part of modern Laois was part of Kingdom of Osraighe (Upper Ossory) and was bit not conquered by the Normans, the rest of Kingdom became modern county of Kilkenny.
Derrane been related to Blathanid distantly make sense in context of Conamara/Árann -- after all one of reasons the language survived as primary language in the Galway Gaeltacht was due to lack of contact/movement from the anglisced areas around it.
Byrne having wide level of matches make sense given history of Dublin both as urban area (thus potential ancestors from all over place) and also given it's history as centre of the Pale. Given that he appeared to have ancestor associated with Fermanagh this could explain his Scottish connection etc.