Well, and see...they can’t ‘magically’ find the black boxes until they ‘discover’ something on the surface, now can they? /s
If the ‘southern’ route hypothesis holds water (pun intended), I predict they will find a debris field in short order and then, within hours, a “Got something!!!” (iow, a ‘signal’).
I’m of the opinion the USN knows exactly where the plane is and that these poor folks (the searchers) are risking their lives sailing through/flying over one of the most inhospitable patches of ocean on the planet looking for debris to justify the location that is already known...
“I’m of the opinion the USN knows exactly where the plane is....”
.
Probably everybody and his mother flying around in that area know where the plane is but were told to keep up the pretense of searching.