Well, you and Atom Smasher mean it that way, apparently. Not so sure that "everyone" in the PUA world means it that way.
Meanwhile, in the real world (as opposed to a pickup forum), this is how smirk is defined, these are the first entries that come up when you Google "smirk definition". I suppose the Cambridge version comes closest to what you are saying. But notice that in most of these definitions, there is a negative connotation to the smirk, a sense of conceit or smugness. Which is what I think of every time someone brings up smirking.
a smug, conceited, or silly smile (Google Dictionary)
to smile in an affected or smug manner
https://www.merriam-webster.com/dictionary/smirk
a smile that expresses satisfaction or pleasure about having done something or knowing something that is not known by someone else
https://dictionary.cambridge.org/us/dictionary/english/smirk
to smile in a conceited, knowing, or annoyingly complacent way
https://www.collinsdictionary.com/us/dictionary/english/smirk
A
smirk is specific kind of smile, one that suggests self-satisfaction, smugness, or even pleasure at someone else's unhappiness or misfortune.
https://www.vocabulary.com/dictionary/smirk
to smile in an affected, smug, or offensively familiar way.
https://www.dictionary.com/browse/smirk
Not so sure I would call Russell Wilson unattractive, not that I'm any judge. Anyway, there are always outliers, and besides it's not my theory. But the point is that good looking people get a lot of positive reinforcement, so they tend to have confidence. It's kind of like what
@redskinsfan92 was saying earlier about confidence being related to experience. Good looking people tend to have positive social experiences, so they gain confidence in social situations. But there are still attractive people who lack confidence.