Well, if you would have started with the less attractive girls, you could have gained more confidence and experience and slowly progress towards the more attractive ones. Imagine a parallel universe where you did exactly that. Which one of these universes would you rather be in, now? (I am not sure if "starting here, then progressing there" was a part of the original advice, but I am trying to be charitable here. It is not necessarily a bad advice, maybe just not explained sufficiently.) Also, the "fat and ugly" doesn't have to be taken into extreme. There are many average girls without boyfriends simply because the boys around them fight for the few most attractive ones. Some of those boys will lose in the competition, and those who win will often get a spoiled princess that will probably cheat on them soon because she will get many attractive offers. If you go for "average in attractiveness, but has a few traits that I personally prefer (traits that are not generally popular; such as being a nerd)", you can get rather close to the optimal outcome... and yet as an overconfident young guy this would probable seem to you like settling down, because you imagine getting a princess plus the traits you personally prefer. Which is not impossible, just less likely, especially if are not one of the most attractive guys. (Similar advice applies to women, too; and most of them also hate to hear it.)

To be sure, even if the selection effect I mention is non-negligible, it evidently isn't strong enough to drive pick-up knowledge to fixation. [...] I suspect I'm missing something but I don't discern that in what you quoted (although it does sound simplistic & exaggerated).