I wasn't aware of any arguing. It's just something people should be aware of, especially if they ever remove the shackle to use somewhere subjected to potentially greater loads.
But in any case, you're right, particularly when it comes to the hitch on the Discovery, which are known for being a little less robust others. But even ideal Class III hitches are only rated at 10,000lbs.

 

This guy is selling the Warn Shackle for $29 Free Shipping. Everyone else on eBay is $60+.

Warn Industries Trailer Hitch Receiver Shackle Bracket 29312 New Free | eBay

 

Ordered one from the above eBay seller today. It has already shipped.