Agree Ian W.
There will be a huge amount of information that has been made available to the SAR teams that they have zero obligation to release to the media.
The timing always did look a bit suspicious. They managed to get the Ocean Shield in location just in time to hear the last signals from the pincers. Well away from the location of the previous aerial search area.
I suspect it is very likely some other data was made available to allow this to happen. The nature of this may never be released. It could be a satellite, or could be JORN.
We don't know much about JORN. Its capabilities are likely understated. It is publicly acknowledged this technology is less effective at night. Defence dollars are tight, and it may not have been operational overnight. If operational, its focus was most likely on maritime traffic (people smugglers) between Indonesia and Christmas Island (i.e. north of Christmas Island) - people smuggling being a key political issue at present.
But maybe it was on.
And maybe it did pick up an aircraft almost 1000km SSW of Christmas Island close to the time of impact. Which does make you wonder about the days of searching well SW of Perth.
Or maybe it picked up a signal much earlier that night on while MH370 was still somewhere west of Sumatra, and used this datum to refine the Inmarsat data. That process might take some time, and could explain the apparent "delay."