I performed some investigations and here are my thoughts.
The feature was introduced in EE2007.6 as a result of this request:
dts0100486803 — DxDataBook should obtain symbol data from the central library
The idea is brilliant as data duplication is avoided. But actual implementation is a bit faulty.
As expected DxDatabook uses "Part Number" property to retrieve symbol data. And when component is annotated from DxDatabook into schematic it also honors mapping between "Part Number" property and database table header name (this is defined in .dbc file). But if you select "Use symbol data from central library" option in DxDatabook configuration (the same .dbc file) and try to make a verification of the component - it fails. After some playing around I came to the conclusion that the reason for it is that verification process expects the database table column header also to be named as "Part Number" (so it doesn't honor DxDB database to property name mapping). E.g. if I have a database table column header name as "cl_partnumber" which is mapped to "Part Number" property in .dbc file then verification fails. If I rename database table column header to "Part Number" - it works.
So perhaps Mentor could fix this issue in the nearest future (it doesn't look complex) so we all could enjoy even higher library data reuse.