How comes they describe that in terms of 'convincing them that you are something you are not' rather than 'becoming something you didn't use to be'?
The given "something" is a package consisting of many parts. Some of them are easy to detect, some of them are difficult to detect. In real life there seems to be a significant correlation between the former and the latter, so people detect the former to predict the whole package.
After understanding this algorithm, other people learn the former parts, with intention to give a false impression that they have the whole package. The whole topic is difficult to discuss, because most package-detectors have a taboo against speaking about the package (especially admitting that they want it), and most package-fakers do not want to admit they actually don't have the whole package.
Thus we end with very vague discussions about whether it is immoral to do ...some unspecifed things... in order to create an impression of ...something unspecified... when ...something unspecified... is missing; usually rendered as "you should be yourself, because pretending otherwise is creepy". Which means: "I am scared of you hacking my decision heuristics, so I would like to punish you socially."
What is it that is difficult to detect in a person and still people care about potential partners having it? Income? (But I don't get the impression that the typical PUA is poverty-stricken, and I can't think of reasons for people to care about that in very-short-term relationships, which AFAIK are those most PUAs are after.) Lack of STDs? (But, if anything, I'd expect that to anticorrelate with alpha behaviour.) Penis size? (But why would that correlate with behaviour at all?)
If it's worth saying, but not worth its own post, even in Discussion, it goes here.