There is a saying in film production: "We'll fix it in post!"

The high number of compositors in the credits of a film shows you how many people were needed to fix 'fake' looking scenes such as this. Compositors easily smooth this out, and add fake environment, hair, clothing, or even limbs to hide the excess green-screen cropping. Also, a well-placed cut to a close-up shot can hide awkward actor movements on poor sets.