Comment by arandr0x

It is possible to do leetcode without practicing, even before AI. That said the structure of the Big Tech process is also quite long/multi-step with many opportunities to give up during, which helps select for drive. It's hard to do this effectively with shorter processes. It is however always a good practice to 1) design very hard interviews but 2) give a lot of preparation to candidates beforehand, even for non-leetcode interviews, as it helps filter who can efficiently and diligently use provided information to increase their performance.