New sub-regions in AncestryDNA results

Another recent advancement by Ancestry on their ethnicity estimates in AncestryDNA is the addition of sub-regions within countries. If this is not new, I missed it before. When looking at my Dad's results, I see an update pointing to Central Ireland, specifically the region of Roscommon and Longford. This is an unfamiliar region. All of the known research about my 3rd-great-grandfather John O'Brien had said he came from County Clare.

Source: AncestryDNA. Updated results for my Dad.

To be fair, Roscommon & Longford are directly northeast of Limerick, where John likely joined a ship that took him into the British Navy. Perhaps this is a more ancestral region of the family, or the home of another Irish branch, such as the Connor family.

Here's another visual courtesy of Google Maps, showing possible routes from Limerick to Roscommon and Longford.

Source: Google Maps.

AncestryDNA also shows how many matches also share a region. My Dad currently has 19 matches who share East Roscommon and Longford. When I look at those with a common ancestor, the result lists O'Brien, Martin, Conner/Connor, and our Allman branches of the tree. As I currently have a brick wall on the identity of my third-great-grandmother, the mother of John J. O'Brien, there's a whole other set of branches that may also connect to this part of Ireland.