I am curious about the technical details of this further INMARSAT ping analysis.
As are we all. I doubt the true explanation has anything to do with Inmarsat.
Most likely (to me) is that another satellite also received the pings, and this allowed them to eliminate the north and to dramatically narrow the southern search area.
The posturing has been very positive for quite a few days. A fairly significant announcement from Aust PM to Malaysian PM based on a couple of grainy images? I don't think so.
They diverted that Norwegian car carrier several days before they announced the first satellite images of debris. And then a large multinational effort with aircraft from 5-6 countries focussed on this (relatively) small area.
They also confirmed that the initial debris had been subject to corroboration by other satellites.