I just went through a long period of job hunting (thankfully now employed) and this post rings 100% true, especially the part about being rejected for inexplicable reasons. The "gotcha" question about Fourier transforms that you last worked with for half a semester in college 10 years ago? That question cannot possibly be a serious qualifier for a full stack dev position. Instead, i suspect it's meant to either (a) make the interviewer look smart to their (possibly nontechnical) startup founder bosses and (b) provide cover for rejecting you for some other reason that can't be spoken out loud, like "cultural fit".

I think you're right. They set salaries low and the bar insanely high, reject a bunch of candidates to make themselves feel like they can be the next Google, then ultimately settle on a lucky person who just happens to be there as they've gotten acutely desperate and given up hope of finding a mythical 10x engineer.