You can't just look at a tier list and have it be 100% conclusive. XFX is all build by SeaSonic, and all their power supplies use quality parts. There are MANY good quality power supplies not on that list, and many bad ones, too.
80+ efficiency ratings mean just about nothing to the normal user. You may see a couple pennies here and there saved between 80+ bronze and 80+ gold, and it shouldn't be used as a judge of quality. There are many 80+ gold units that are lower quality than some 80+ bronze units.
And the whole +12v rail meaning is vastly misunderstood. It's not something that physically provides power, it's a group of traces monitored by the overcurrent protection. This actually can lead to problems on a single +12v rail, as a single part could draw too much power without actually tripping the OCP circuit, and damage a part. This is rare, but as no single card pulls more than around 24a at completely max load, and around 30-35 for the entire system, having 62A doesn't really mean anything more than having 50A when using a single GPU.