The Mopar kit does the exact same thing as the Teraflex (JK only) or EVO hinged tire carriers. On all 3 of these solutions the weight of the tire is carried by the OEM internal hinge mount support structure, meaning the internal parts that the actual hinge parts bolt onto on the passenger side of the Jeep. These OEM support parts are strong enough to carry the weight. The OEM hinges themselves are also strong enough to carry the weight. The separate Teraflex (JK only) and EVO hinge parts that bolt onto the internal support structure may be stronger than the OEM hinge parts but that is not necessary even if it could be demonstrated since the factory parts are plenty strong. The Mopar tailgate reinforcement plate spreads the weight of the tire/wheel over a large area of the tailgate which prevents flex and creasing the tailgate metal. This is the same principle as using a big washer to spread the weight when bolting something to sheet metal that would bend the sheet metal without the big washer.
The JL tailgate is stronger than the JK tailgate for the reasons stated by Eddie in his video about mounting his 37s on his JL. In fact Eddie ran his JL without any reinforcement other than the LOD tire raising kit on at least several wheeling trips without a problem.
As to the Mopar kit I do note that bump stops between the tailgate and tire are super important to prevent the tire from moving going over bumps, Eddie explains this in detail in his videos as well. I can tell you that the Mopar bump stops work great, I have virtually zero tire movement closing the tailgate or going over bumps. I am not a major rock crawler like Eddie but his JL handled plenty of major bumps without any of these kits so the OEM tailgate is plenty strong.
Don't get me wrong I am not saying anything negative about the EVO kit for the JL, it looks great and I would have probably bought it if it was available when we got our JL.
