> a single person would be able to write it

I don't understand the distinction. A single person can't really write a code now, if you'll disallow ML libraries. You need a complier, libraries, an OS, etc. The vast majority of us work in the highest levels of abstraction possible. That's where the practicality and productivity is. I don't think he's saying "Anyone will be able to sit down and write it in assembly". I think he's saying, it will make sense when it's written, with the abstractions as they are, with hindsight clarity of "we just had to...".