Yes he did that. There's a camera very close to the floor by the sofa. While almost everyone was in the hot tub, Simon and another were talking by the camera and he just pulled down his pants and spread his butt cheeks right in the cameras view.
And apparently he got a boner a few days ago during a party och showed Judith and Pontus. They were very eager to see it also. Judith is gay and Pontus is not.