Okay I know I may open a can of worms on this but wait before responding on the one-step crossover technique/style of throwing javelin.
If we can get past that one cross-over step before the throw could be marginally successful - what would be the harm of stepping behind with the non-plant leg of the throw? I.e. Right handed javelin thrower cross-over with the right leg/foot is behind the left just before left plant and block.
Could this help with the wrap style of javelin delivery and allow for a more natural left foot plant? Having said this - I coach NCAA division 3 athletes with limited exposure to javelin throwing before the age of 18, strong backgrounds or a strong visual connection to MLB-hardball baseball pitching. NCAA division 3 athletes also have limited amounts of practice by NCAA rules. I am trying to help hthese type of athletes learn to throw well with limited time and exposure to the event within a relatively short, about 32 weeks in 4 years, direct coaching time.