Too much awe of technology by decision makers who didn't understand it?
As a techie who also has SAR experience, I think there is very strong evidence that the techies are right.
The INMARSAT ping data is pretty good - I doubt anyone just made it up for fun. Even more important, the detection of underwater pings is very close to conclusive - especially since it is almost precisely in the spot predicted by the INMARSAT data. Information provided (including a video of the detection waterfall) makes it an extremely high probability that this was a ULB. Since there aren't a lot of missing ULB's in the world, especially in the south Indian Ocean, this means that they very likely have localized the wreck. They just haven't pin-pointed it yet.
I would guess that, if the initial small search area doesn't turn it up, they'll do what SAR experts normally do: recalculate the probabilities. This would yield a likely search area just outside the initial area, along with some probability that it was in the initial area but missed.
The only even faintly plausible explanation for the aircraft not being in the south Indian Ocean requires either massive incompetence of initial and reviewing authorities, all down the line, or a massive conspiracy. This I relegate to very low probability (<1%).