You can do 100% of the legal ass covering that you need to do, with performance evaluations, pips, and careful documentation.
I’m not convinced that stack ranking is a good solution to this problem. A good organization and HR team knows how to terminate someone who is not performing well without incurring legal liability.
It can be a somewhat drawn out process, but a stack ranking system doesn’t seem like it would make it a lot faster to me.
My gut is stack ranking came about because a business school graduate realized that performance is probably distributed among a bell curve (it probably is), and if you could continually prune the worst performing 3% of the org you could continually improve the quality of the remaining workers.