Re: "... replica plane parts having been set adrift.."
If you read the report they are taking such elements into account. Rather than trying to work out where the bits individually went, they use ensemble simulations that are showing where the bit can't reasonably have started. No debris found on the Oz coast - eliminates a whole set of possible starting positions. And so on. It looks very much as if they need to start looking north of the area they searched, not by much but some.
Overall I'm impressed (and a teeny bit proud) at very solid work done.