Sure, it shows that you can apply yourself to a task and finish it. That's also what a college degree shows, but at least there you learn something useful. Come to think of it, that's what any stint over a year or two at a company can show, too.

It's not predictive of the traits that mark a successful IC in my experience. I'm talking about areas like project planning, professionalism, large-scale system design, personal ownership, meticulousness, etc. Curiosity. Some of those might tangentially be covered by leetcode but I guarantee you important stuff isn't.

Everyone I've seen to fail, either via PIP or otherwise, has cracked these interviews. I've seen many fail over the years. Even worse, I've seen many whom I know would be strong performers, wash out because they got the wrong DP problem that day. Where's the benefit in a regime like this? The company loses and good candidates lose, too.