Additionally, the reasons for delaying lowering the gear until 1000' are:
Capts ND is lost (older-style RATs, most likely on the msn's quoted above)
and
The a/c goes into Direct Law with selection of gear down, so auto pitch-trim is lost - you will see "use manual pitch trim" in amber on the PFD. Hence, Airbus consider it better to be in trim for landing (Conf 3) prior to lowering the gear.
DCD