No, I am not missing any point.
The fact of the matter is, they have not found and authenticated any wreck site as of yet.
A missing tag, a series of interviews and a map is no more evidence of Earhart's demise than aircraft parts and a sextant case (found by the British) is.
The alledged P&W R-1340 engine is not unique to Lockheed. Fokker, Boeing and others used that engine in civil transport aircraft before the war.
So to summarize: New Britain is one of several theories.