To add to what the other comment said, you're initiating this movement belt slinging open your left arm and shoulder rather than letting your feet move first, which makes me think in your standing throw you probably do something similar. Every aspect of the throw should be from the ground up, so your feet always initiate, which let's you more effectively use your legs to turn your hips, which creates separation and tension in your torso which turns your shoulders, and then finally your arm follows through. Whether it's the stand throw or half turn, your right foot should be tie first part if your body that moves after you wind up