This is based on a real use case of mine, it was very difficult to identify that "Johann Hubert Stammen" who only had references to Germany and a wife he married there was the same as the "John Stammen" my DNA match had as their last known ancestor. John had no reference to Germany other than the country itself from a Census record, he married another (German) women in the US and had even more children with her. So surely a case where you normally would say "Could be but no proof".
It's the perfect example how traditional genealogy (using Census data and church records) is making a huge leap forward when it's combined with DNA testing. This merge would have been very difficult to prove if not for DNA testing which fit not only into both family trees but also fit the expected DNA shared percentage.
This video shows the merging of family trees between a DNA match and myself. Powered by Artificial Intelligence algorithm it has traversed both family trees and notified the user that a potential match was found between a "Johann Hubert Stammen" in my family tree and a "John Stammen" in the family tree of my DNA match:
More pictures of the family tree data before the join in the above posts. Hope that convinces many more to take a DNA test.
Disclaimer: I'm the author of the app used in this video: