http://data.stackexchange.com/stackoverflow/s/1323/ownerdisplayname shows that many posts have a OwnerDisplayName field that is different from the user's current display name (which is what the SO web site actually shows). The same is true for LastEditorDisplayName. What is the reason why this discrepancy has not been corrected?
The Stack Exchange Data Explorer is not live but is only updated monthly (if that). Thus, changes in the intervening time will not be reflected.