Even if MH370 crashed on the north side of the search area, in ocean current simulations the debris still fans out about to some 1700 km wide by the time it gets to Mauritius / Reunion Island.
Since Reunion Island is only 70 km across, there is only a 4 % chance of any debris from MH370 ending up on Reunion Island.
If this flaperon is indeed from MH370, we are either extremely lucky, or there is a LOT more debris from MH370 still floating in the South Indian Ocean.
If the latter, we may wonder why none of that debris was found in the earlier searches back in March/April 2014, much closer to the crash site...
Maybe we were looking in the wrong place back then ?