L.C.
My son did the same thing. He eventually saw his dad standing up to go potty and switched over. He never fell in. It's probably what is easiest for him and what makes sense. It took awhile before my son pooped in the toilet too, but eventually he did and he sat down when he started. I would just say to relax a little bit, and let him stand there. If he falls in, just pull him out and wash him real quick in the bathtub since he is already naked. It is a learning process. He won't be there forever. Good luck.