A bit of a logic fail in that article, typical of the standard of modern journalism
Kind of. I think what they're implying is that, if they don't find the plane in the priority search zone, that raises the possibility that it glided some distance rather than spiralling down when the fuel ran out, spiralling having been their working assumption so far in setting the priority search zone I believe.
Here's a new BBC article, although IMO the announcement looks slightly driven by a desire to tell the relatives what they want to hear -
MH370: Search for missing plane to be suspended not shut down - BBC News