Checking a couple of other lever guns I have (neither a long ranger) there's enough "click" to keep the mechanism shut when you close it, until you deliberately lower the lever. And that can be done even with the hammer cocked. Since the lever is linked to the bolt, lever up equals bolt forward, lever down equals bolt open, and closing it leaves the hammer cocked. I've never seen a healthy lever gun whose lever just fell open with its own weight yet. But maybe their lawyers don't want it staying in battery while you're not holding it with a proper shooting grip?
I could see a well-worn or slicked-up gun having a very loose lever, but it sounds from what you're saying that you're handling a new firearm. Mine aren't new but they're not far down their journey yet either.
It was meanwhile occurring to me that a .223 Long Ranger set up to take STANAG magazines could be the ideal plinker.