I beleive the first mention of this, was in a post-war novel "Spy for Germany" (Spion fur Deutchland) and it's been drifting around ever since.
The problem with the "folding winged Ju87 launched from a submarine" version, is that the only submarine big enough to carry a Ju87T (assuming that any Graf Zeppelin Stukas were left by 1943), is that it would take a Japanese I-400 class sub to transport them (after modifications to the Stuka).
The Stukas could have been disassembled and transported by sub and reassembled at their destination, the Germans transported quite a few aircraft to Japan this way or transport them via cargo ship to the destination. Either way, there would need to be facilities for offloading, assembling/prep work and such.
This would be a difficult undertaking to do in total secrecy and still be within range (even one-way) of the Pacific side of the Panama Canal.
It makes for a good story, though.