A320 with CFM and IAE are completely different in the flare. Advises for one type don't fit the other.
On the IAE you can idle the thrust at 50' no problem, especially with Sharklets. Any later than 40' and you'll land long.
On cfm I would advise against flaring the thrust before 20'. Even then it is easier to land the thing by reducing the thrust slowly - unfortunately difficulty to do if you're using A/THR.