This is listed as by design in the microsoft knowledgebase article Q167186
"PRB: SET CENTURY ROLLOVER Ignores Setting of SET CENTURY OFF". There is a workaround in the article...they say "The reason for the display of the year in either a two or four-digit format is to differentiate which century the date belongs to."

To be honest I'm not fond of displaying two digit years close to the end of the century, just because the user has no easy way to see if what they entered is correct, just my opnion though....