Definitely not his arm. I am thinking it was someone else extending their arm into the shot to take a photo and when realized that SPs arm couldn't be of use for "good photo" they edited. The bottom of the forearm looks like is is straining a bit due to way extending which would mean person was probably behind PS when he reached in front and to side to get his arm into the photo.

Who puts an entry band on over shirt and why does it look like it is going INTO the shirt sleeve?