I know nothing of this incident, but I do fly the 330.
For reasons known only to Airbus, below 400 ft radio height the autothrust logic changes. Thrust response 'relaxes', rather than trying to chase the speed. Any small increase - or decrease, crucially - in IAS does not provoke a change in thrust.
If speed falls a long way, there is a thrust response. But thrust levels on the 330 on approach are very low anyway as it's all wing. Furthermore, the three-spool engine configuration means thrust builds quite slowly.
The net result is that below 400 ft, by the time the autothrust responds the speed can be very low - I've seen 12 kts low - and whilst N1 is increasing, there is little increase in thrust.
This normally becomes a problem in light winds, particularly with gentle tailwinds on approach.