Research has shown that the body only contributes 10% of power to the golf swing, whereas the speed of the hands and their actions contribute 90% of power.
Further “transferring” your weight from the back foot to the front foot creates only 2mph of body speed – which only increases clubhead speed if your timing is inch perfect.
In exercising for golf my focus is always on the forearms. This practice was further given endorsement by no less than the 2005 REMAX Long Drive Champ, Sean Fister, when he came to visit in September.
His words to me were: "I don't train anything above the elbow joint. Jack Nicklaus said that I have the fastest hand speed of anyone he has ever seen."
Look at the following attached.
This is a very clear view of the anatomy of the forearm. The most important muscles I feel are those that help cock and uncock the wrists and those that help pronate and supinate.
Work on those
I did these exercises plus master the Snap Release10-24-E only in April of this year and the results have been very very satisfactory.
Indeed the muscles you pointed out would cock and uncock the wrists and pronate and supinate. Although muscles of the upper arm would also help in pronation and supination of the forearm- so if you were trying to strengthen those- then you would want to also strengthen the upper arm muscles. However, none of the muscles that you described would move the hands faster through space. So to me, Sean's quote is just another quote that doesn't make any sense or is very unclear.