E.g. here—the original statement was 1932-01-01T00:00:00Z with precision 9, i.e. the year 1932; the value merged in is 1932-00-00T00:00:00Z with precision 9, i.e. the year 1932 as well. These values are different from the technical point of view, but from the user’s point of view identical values are not merged, which is bad user experience.