OPEN DES is correct - Thales New FM Pilots Guide Release 1A
"Position update
NO GPS [A/C CONF]
Aircraft with no GPS: An automatic position update at runway threshold is performed when the thrust levers are set in the take-off position. If a take-off shift is entered in the PERF TAKE-OFF page, the FMGC position is updated to the coordinates of the take-off shift.
GPSOPT [A/C CONF]
Aircraft with GPS: No position update occurs when the thrust levers are set to the FLEX or TOGA detent."