Not necessarily, French may never confirm nor deny it, if they are looking for serial numbers, etc. and there are none then what remains is just a conjecture or best guess. Actually Australians stated very carefully "in all probability this flapperon .... ", they may never be any 100% positive proof. Unless you believe that someone on purpose put this piece there on the beach 99.99% is good enough and this is exactly what Australians (and Malaysian PM) are saying.
I'd like to see Boeing validate this as well via serial numbers (if any can be found).