[DougMerritt]

I started with Bell Labs Unix, transitioned through many variations, and then when I came to OpenBSD and Linux, they were both pretty straightforward compared with, say, porting to or from System V Unix.

I don't think you're wrong about anything. It's true that one may need to pore over kernel code, and yes, often you have the "duty of knowing how the specific Unix was implemented". I just that that you're over-emphasizing the difficulty.

Life is hard (including programming), but that's where we calibrate our zero setting.