I do believe the primary purpose of the 3 position safety on the LC and a few other makers was to allow the option of using a resetting safety or a "hunter's" safety, which resets.
I cannot say as I have ever heard of the purpose being to uncock the gun while open. And why would one want to uncock a gun when open? Just do it closed, and if you have a gun without a 3 position safety and the gun is broken down, then just trip the lever closed.
I once came across an LC that someone put a bead of solder behind the safety button as to prevent it from going back to the third position.
