An easy way to get two leads for free. Place a boat on the ground or in the water, and push the llamas into it. The lead pops out, and the player can continue to even take the llamas.
... Leads are valuable, right? They're valuable to me anyway. I can never find the slime needed to craft them.
Pretty sure that's intended; that's just the wandering trader dropping his leashes; he does the same when he is killed.