There doesn't seem to be an appropriate forum for this, but this seemed closest.
Someone I know claims that they get more roundoff height by bending the arms, and that gymnasts don't get good height out of their roundoffs. I have a feeling that it's just because they don't know how to push with the shoulders and haven't seen a good gymnast do a roundoff for height.
But then I realized I haven't seen it either. Elites never seem to do their skills directly from a roundoff, and the person I know gets more height his way than the random amateurs on youtube. Does anyone have a link of someone getting massive height from a correct form gymnast roundoff?