My take is that's the limit on the stock rails and crossbars which are pretty weak. I have a Sherpa on my 2021 and it definitely can handle more than that. The bolts and mounting on the 4Runner are pretty stout built.
How does the hybrid work on overpasses/uphills at highway speeds? Does it kick in to keep from having to put your foot into it/bunch of downshifting? Currently have a 2021 ORP towing a trailer with my Kawasaki KRX1000 side by side which is 3500-4000lbs total weight. I have to lock in 4th gear...