I converted a crappy old PHP code base to a modern one by breaking down their product and re-building it, re-using assets as I needed. It took a lot of time and extra work but I did just that.

You flatter me by thinking that comment comes from a place of arrogance. Assume the aforementioned codebase is complete garbage coded by two non-programmers. It's an MVP essentially.

It's not like I worked somewhere like Facebook and re-did their infrastructure. I remade the work of two business guys.

Why? You just sit there and work, 6 hours isn't a very long time. Maybe I have a unique ability to stay focused for hours on end.