About 10 years ago, I remember a guy that interviewed that bragged that he wrote his own linked list class instead of using the one the STL used. I was amazed

About 10 years ago, I remember a guy that interviewed that bragged that he wrote his own linked list class instead of using the one the STL used. I was amazed and impressed at the time. Now that same statement would totally set off red flags and he'd be a non-hire (unless I could personally audit the code). Maybe he provided more syntactic sugar so his implementation was easier to work with? And if that's the case, why not just build on top of the standard implementation? But if he claimed a performance increase, is that for the general case or for some specific case he was coding for? Deviating from the standard library is a bold claim that has to be backed up by a code audit.