Re: "Hopefully he also added a bit of text along the lines"
"Developing in UNIX is like flying. Developing in OS/400 was like hiking up a mountain. Either way you achieve some altitude, but it's a very different experience."
When I'm flying I prefer to go well over the top of the mountain, or to go around it completely ... Come to think of it, maybe your analogy is more apt than intended :-)
In the time frame of TOA, un*x/POSIX wasn't an option on the AS/400 (outside of Armonk, perhaps ... and maybe Murray Hill ... the BSD world was working on it, of course).