relevance of last update date in supplier purge in 11i

Hi,

We are trying to purge some old inactive suppliers in 11i. The AP user guide indicates that

"You can purge suppliers that meet the following criteria:

• Supplier is inactive, and the values of Inactive On and Last Update Date are on or before the Last Activity Date you specify"

Yet, when I run the purge with Last Activity Date = 31-DEC-2001, it selects (for example) a supplier that has po_vendors.LAST_UPDATE_DATE = 26-FEB-2002 and po_vendor_sites_all.LAST_UPDATE_DATE = 27-JAN-2015, both LAST_UPDATE_DATE being AFTER the Last Activity Date specified, i.e. 31-DEC-2001 (so they shouldn't be selected to be purged according to the user guide).