So the 9900KS has an all-ore turbo of 5 GHz (300 MHz higher), and, minimum base clock is now 4.0 GHz (400 MHz higher); those are significant jumps, but, whether it will hold off a Ryzen 12 core in content creation is another story...(seems doubtful, based on some recent leaks on how well a new lowly 6 core is scoring in Geekbench, if the leaks are accurate)
As to the original 'binning' question, these are the CPUs that have proven stable at higher base and turbo clock speeds, and therefore are designated as a new model variation. (Makes sense, given the number of overclocking enthusiasts seeking a perceived all core 5 GHz utopia...)