Yes that is special heavy duty one with a WLL of 6,670. The standard 4" are 5,400. Still a far cry from 40k.
You have to be careful too when tieing things down about the attachment points. For example on my Fontaine trailer if I wrap a chain around a chain spool or stake pocket it is rated for 5,400lb. The rub rail where you hook straps is only rated for 5,000lb. This is a heavy duty trailer that weighs over 15k empty. I bet most smaller trailers don't have attachment points rated this high unless it is a d-ring or something like that. I doubt the rub rail on a trailer made to be hauled with a pickup is even good for 5k.
You have to be careful too when tieing things down about the attachment points. For example on my Fontaine trailer if I wrap a chain around a chain spool or stake pocket it is rated for 5,400lb. The rub rail where you hook straps is only rated for 5,000lb. This is a heavy duty trailer that weighs over 15k empty. I bet most smaller trailers don't have attachment points rated this high unless it is a d-ring or something like that. I doubt the rub rail on a trailer made to be hauled with a pickup is even good for 5k.