Video up on Youtube from Spanish? Television clearly shows it is a bow. The Saudi’s protocol director appears at pains to bow as well so as not to extend the gaffe.
Obama bowed.
You mean the man at the king's left? He looked like an interpreter. And he looked like he was blindsided by the gesture; like he expected to translate some pleasantries, and the bow was so weird to him he didn't know what to make of it for a moment.