Yeah, it’s just bro science brah
“Orthopaedic surgeon Dr. John M. Kirsch, conducted research through a series of CT scans performed in 2004 to study the mechanics of the hanging exercise in the shoulders of live subjects. The study found that this simple exercise called relaxed hanging aka ‘brachial hanging’ was helpful in certain shoulder problems.”
“John M. Kirsch, an orthopedic surgeon, says that 99% of shoulder pain can be cured and prevented by simply hanging from a bar. By performing a dead hang, the space between the acromion (bony articulation of the shoulder blade) and the head of the humerus (upper arm bone) opens up, potentially relieving any impingement of the rotator cuff tendons.”
Climbers, gymnasts and others have found it helpful for a long time beyond the grip strength component. I personally choose to go the non surgical route for rotator cuff issues (with guidance from my ortho doc) to see if I could resolve my issues without surgery. 25 years later still no surgery and dead hangs are part of that success.
But I’ll give it to you that farmers are great and likely just as important for shoulder work.