How the tiers are set
We place every processor in a tier by its gaming index, where the Ryzen 7 9800X3D is 100. S is 85 and above, A is 70 to 84, B is 55 to 69, C is 40 to 54, D is 25 to 39, and E is below 25. The index measures how fast a chip is in games at 1080p, where the processor is the limit, not how fast it renders video.
That is why chips with a lot of cache rank so high. Games are sensitive to cache, and the X3D line from AMD beats chips with many more cores in most titles.