This is the simplified version, (which fits how my brain works), vulture hocks are recessive, requiring a copy from each parent to produce a chick with full blown vulture hocks. Birds that look prefectly normal may still be carrying a single copy. So a bird that has visible vulture hocks, having two copies, can not help but pass a copy on to all it's chicks, and should never be used as a breeder.
This seems to most commonly come from crossing with Cochins, whose massive soft feathering can often cover this fault. Overseas vulture hocked Brahmas are allowed in many countries, which would be easier, as it takes considerable effort to breed it out.
In reality it is more complicated than that, there are likely three genes and other modifiers at play here. Bottom line is don't use birds with vultire hocks in your breeding program if you ever hope to get it out of your line. Even clean hocked birds can produce VH chicks, if it is in their familly line.