It's as if you didn't read the comment I wrote and started foaming at the mouth at the chance to say RTFA as is HN tradition. (Or didn't read the article closely enough yourself)

He said explicitly, he used a debugger.

He came to understand the value of having a proper mental model of your code, but the comment I replied to said they had never used a debugger.

My comment was about the difference between knowing how to problem solve without a debugger, and straight up never having used it

There's nothing wrong with having more tools in your toolbox