However it leaves it to speculation that Hughes is an inventor. He just didn't make the first jetpack and that was it. He had to again speculation build a few prototypes before finalizing the one we see in The Rocketeer Movie.
There were at least 2 earlier prototypes, but they would have been destroyed in the same accidents that killed the 2 test pilots. I just don't see the need to retcon when the movie tells us where the next version of the pack is coming from.