Does the shooting script say Obi-Wan is making a dragon noise or was this made up after the film was finished?

Watching the scene, I just don't see how the Tuskins are supposed to think Obi-Wan is a dragon. They turn and see him coming, waving his arms. They run because they know who he is. This gives the impression that the guy in the hood is respected and feared and not to be crossed. The 'Dragon Call' seems to be a SE explanation that, like Greedo shooting first, ruins a character introduction and story element.