I think Noah's point was that homebrew wasn't a simple tool. And, not only was it evidence of the developer's capabilities but it was also used extensively by all of the employer's own engineers. A tool they all relied heavily on to get their own jobs done. Making it clear he could create software they found important for their own production. And, made it possible for them to deliver service to billions of users.
He got nervous on the whiteboard when asked a relatively simple question. They proceeded to shut him out of the position, completely disregarding his ample qualifications signified by their extensive use of his product. Which is a kind of tragedy.
Comparing an A/C unit to rocket science isn't an equivalent comparison. I can't think of a good analogy to be honest, but that isn't even close.
No other field I can think of really has the problem ours does. You can either make A/C units and rockets, or you can't.
But, in software engineering, it is highly possible to be able to say..... develop high quality GPS mapping software from scratch used by the Navy. Then turn around and have a company making word processing software reject you because you couldn't write a Mandelbrot fractal generator from memory on a whiteboard with a marker.
The fractal generator has zero to do with their word processing product and will never be a useful test of your abilities. Clearly the guy who made GPS mapping software can figure out how to write a word processor. Not to mention, they already have the word processor written so he'd only be assisting them in maintaining their existing code. In other words, he's already demonstrated his ability to write and maintain code of a high caliber. None of it makes any sense.
I really don't think any other field has this issue. It is weird as hell, and unusually pervasive in our culture.
Edit: It won't let me hit reply on your comment below. I think we've hit the maximum length for this comment thread. But, I'll respond by saying I don't know what position he was applying for. I'm not sure he ever explained beyond that tweet. The first I heard about it was Noah mentioning it. But, if it made their lives easier so they can deliver products on time to their own customers it makes sense they have a position somewhere in their company that would be a fit for him. At the very least it proves he is a good developer. Massive systems like the ones Google creates are made by many good engineers working together to make it possible.
The point was they knew he was a good dev.