Earlier quoted context omitted.
Do you think any programmer really understands how their program works end-to-end? At some abstraction layer, we're all clueless. There are many layers between what you type into the text editor and the actual CPU ticks that make your program work. I bet nobody fully understands the whole stack. Now that that text editor accepts English, we're all calling each other names, etc.
While most don't, there are developers who actually do understand systems from end to end. Most developers are terrible developers, compared to the really good ones.
The last time intel made a CPU where the entire thing could fit in one persons head was probably the 8086 or thereabounts.
There is no one developer or engineer at apple that understands everything going on from key press to bits moving around to print the characters I see when I type in this text box.