The non-stop flight from BOM to NRT is indeed non-stop. However the return flight, which is designated non-stop too, stops for a while at Fukuoka. Is this some kind of technical stop?
I'm presuming you are referring to NH943 from Tokyo Narita (NRT) to Mumbai (BOM).
During the winter months this flight does indeed make a technical stop at Fukuoka on the NRT-BOM leg, which is required due to the combination of the distance of the flight, the headwinds normally experienced during winter in that direction, and the fact that ANA chooses to use a 737 to fly this route.
The return trip (BOM-NRT, NH944) does not require a stop due as the winds are beneficial in that direction which means that the aircraft has the range to make it in one hop.