Well, they're hopefully a bit more diplomatic than that, but the truth is Aunt Nell may have been a bit unreliable where certain dates were concerned. Good genealogists check the written record, documenting who their ancestors were and their place in the family. Evaluating documents is tricky business. Sometimes it requires a bit of backbone on the part of genealogists who must question the work of others, often a beloved aunt or uncle. Many accept on faith whatever connections family genealogists have made.
Faith has little place in genealogy.
Documentation is the standard. These and many other documents are the foundation of genealogical research. I'm sorry to say that much of the genealogy in the Family History Library computers in Salt Lake City contain little, if any, documentation of links. This is no slam. The folks who run the place will tell you the same and caution that we need to check out the documentation.