An 1890 era family genealogy indicated an ancestor died after 10 April 1811. No source or reason for the date is given. Apparently one genealogist, also without giving a source, decided to use that as the death date. So now an unsourced "dead by date" has become an unsourced death date.
Indicate where you obtained material and make certain you don't indicate something says more than it does.
Or you could be correcting the error forever.