Short answer: No, it's not a bunch of BS. Theoretically very sound.

It's very different from "penis enlargement" because "penis enlargement" suggests that the penis is enlarged while the rest of the body stays the same size. This technology only works because (a) it takes a lens from a larger (135) format and uses it on a smaller (APS-C) format, and (b) it utilizes the big difference in the flange focal distance between SLR (EF mount) and a mirrorless (E mount).

Making the lens focal length 1.5x shorter and adding 1-stop in aperture while moving from FF to APS-C is, in fact, only letting that lens act on the APS-C sensor exactly as it would on FF. Really, it's not even magical.