Watched an interview with the producer, and have to say that he's poorly informed in at least one regard. Specifically, he stated that the US was not working on anything remotely similar until the 1970's, but that is patently false. Jack Northrup began working on a flying wing concept much earlier. In fact, his multiengine flying wing bomber was in competition with the B-36, well before the 70's. It lost out. Stated reason as I recall was a concern about stability; this was before the fly-by-wire technology that aids the F117 and the B-2 pilot in controlling their aircraft. However, my dad (retired aerospace defence contractor that actually saw the Northrup flying wing during test flights) believe it was just too radical looking for the USAF bomber mafia.
The 229 would have been a pilot killer, as it also would have suffered from some serious stability issues. The flying wing design's primary draw at the time was not stealth, but fuel efficiency and payload capacity. However, it certainly would have been more stealthly than it's comtemporaries. Had they had stealth in mind (and understood it as we do today), they would have had metalized the cockpit and burried the engines in the wings (snaking or baffling the intakes to prevent specular reflection off the engine face). The intakes and the cockpit are the most broadly EM scattering features. Doing that would have reduced the radar scross section by 50% over it's contemporaries, instead of the 20% estimated from the testing they did on this model.