He said that he 'fell off' the horse because his left foot lost the stirrup.
From my own viewing of this, I'd say he definitely jumped off to the left of the horse. He actually uses his left foot, clearly in the stirrup, as his springboard. He swings his right leg over the horse's back before springing clear. After landing on the grass, he appears to collapse into a huddle.
As an accident, it look's very unconvincing.
JaX
