"Phase advance" has been deleted from all up-to-date FCOM / FCTM.
Depending on your variant, msn and engines, if you still elect to use the "phase advance" technique, in some cases (old CFM msn) A/THR will disconnect and remain disconnected below 100' RA...in that case good luck to you to recover a positive speed control before you touch the surface of the Earth.
In other cases (latest IAE), A/THR will reactivate as soon as your thrust levers are back at or below CL detent.