I'm not sure our observations are consistent. What I'm saying is that I've seen many times people who crush the DSA problem, but struggle to define clean APIs, write clear, maintainable and extensible code, or just design systems. In fact in some cases leetcode makes this worse, with it's emphasis on very terse code (e.g. single letter variables, all code in a single method, hard to understand coding constructs...).
About your second point, not to be a dick, but if someone on my team sent a 1k loc single PR for a big feature, I would sit down with them to have a conversation about why that is bad (I have indeed done this before).
About your second point, not to be a dick, but if someone on my team sent a 1k loc single PR for a big feature, I would sit down with them to have a conversation about why that is bad (I have indeed done this before).