Interesting though a visible decapitation probably wouldn’t have fared well in a PG Movie. I always found it interesting that the Lost Cut had the right arm on the floor but then they changed it for the final cut… Has it ever been revealed why?
Interestingly I am looking at the editing at this moment and the footage that is in the film… Is the Walrus Decapitation version although you only see the Arm severed as an end result.
Basically Evanzan get’s swiped across the chest which also get’s Poda Baba as he falls to his knees (this is where it cut’s) The light saber blade is missing coming down behind Ponda Baba or Walrus man as I used to call him. cut to Luke then back to the head.
So apart from a missing element and a few extra frames of Walrus on his knees and the decapitation shot end result it’s all pretty much there but what they did was repeat Dr Evanzans reaction to Obi-wans strike to cut short the decapitation bit. We would not have seen his head come off only the light saber coming down behind his head while he was on his knees. Luke astonished. Head on the floor.
There is a take with Obi-wan with his sabre lowered after the fight rather than upright so this may have been the logical position after the decapitation (off screen)
Also Dr Evanzan is gripping the Walrus neck so it may have been planned that he release the dummies Head.