I have never needed to manually add thrust in the flare, but have allowed the A/THR to do it for me on a couple of occasions, and I have manually added thrust at about 500' on a couple of occasions.
There is a video on Pprune somewhere of an A320 that did have to manually add thrust in the flare just before retarding the trust levers, and we discussed it then.
There are two ways one can take manual control of thrust. As you say, the "phase advance" method is not now recommended by Airbus, probably because doing so can bring consequences which some pilots are unaware of and could destabilise the approach in the wrong hands.