As amusing as this thread is might I interject?
What Musk did was the Bellamy Salute, which was used in the USA until 1942, when it was re-codified.
"On June 22, 1942, at the urging of the American Legion and the Veterans of Foreign Wars, Congress passed Public Law 77-623, which codified the etiquette used to display and pledge allegiance to the flag. This included the use of a palm-out salute, specifically that the pledge "be rendered by standing with the right hand over the heart; extending the right hand, palm upward, toward the flag at the words 'to the flag' and holding this position until the end, when the hand drops to the side."
Congress did not discuss or take into account the controversy over use of the salute. Congress later amended the code on December 22, 1942, when it passed Public Law 77-829, stating among other changes, that the pledge "be rendered by standing with the right hand over the heart."
https://en.wikipedia.org/wiki/Bellamy_salute
It appears that the salute was commonly used to pledge allegiance but at the outbreak of WWII in the U.S. it was thought too similar to a fascist salute. It was suggested the right hand over the heart was sufficient, which is used today.
Now, whether Musk knew this and is deliberately trying to bring it back or not is a moot point on which I cannot comment.