Essentially and probably the same thing. I say probably because I don't know, and haven't reviewed the technical details of the Asiana accident. On the Bus the names and modes are different but the results are similar. The equivalent of FLCH, flight level change, on the Bus is Open Descent or Open Climb, "OPEN CLB", "OPEN DESC." There is no separate button, you pull the altitude set knob to engage the open mode.
If some form of descent is already annunciated, like rate descent, then going open simply asks the auto-thrust to go to idle and the speed could either be managed, MCDU computed approach speed, or other, or pilot selected. The problem is that there will be no vertical event to get the mode to change, except for contact with the ground. If the FCU altitude is set above you, as it was with Asiana, then there will be no intercept, except for ground contact. There is no Glide Slope capture to force the FD/AP and system back into approach speed mode, so the aircraft will simply sit there at idle on speed until it hits the ground.
At AA in the limitations section of VOL 1 OM 1.10.1 - Open Descent - The use of Open Descent, "OPEN DES", is prohibited inside the FAF, or below 1000 feet AGL during a visual approach. (A)
Additionally, you can recover the use of speed mode by simply turning off BOTH flight directors. One of the idiosyncrasies of the Airbus is that if there is flight director guidance on either side and you are in open climb or descent they will stay that way as long as at least one FD is on. You must turn off both or the MCDU will direct the selected mode to the working FD side. Flying a bus in with one FD on and the opposite on off will not go well. The logic of the airplane is to seek MCDU / FCU guidance when it can. When there is no guidance, the system defaults to speed mode and the thrust levers will simply move to hold speed. You push down the thrust goes towards idle, you pull back, thrust increases to hold speed. This is the only acceptable mode during a visual approach.
If there is no glideslope, either ILS or RNAV generated, on a visual approach; turn the magic off, or it will try to kill ya.