Rocky and Karate Kid aren't good examples because both stories are about underdog characters who's will and determination overcome their lack of skill.
Sure, we could argue about whether that assertion is correct but these comments demonstrate that at least half of the equation seems to hold.
I'm just pointing out that the article incorrectly interpreted Rocky and Karate Kid. The article says that Karate Kid is misleading because it shows people achieving expert skill in two months time. The author is incorrect because Karate Kid (and Rocky) didn't succeed based on their skills, so it's not relevant.
Did you see this New Yorker article on how the underdog can win? http://www.newyorker.com/reporting/2009/05/11/090511fa_fact_...
An interesting quote from that article:
What happened, Arreguín-Toft wondered, when the underdogs likewise acknowledged their weakness and chose an unconventional strategy? He went back and re-analyzed his data. In those cases, David’s winning percentage went from 28.5 to 63.6. When underdogs choose not to play by Goliath’s rules, they win, Arreguín-Toft concluded, even when everything we think we know about power says they shouldn’t.
Being presumed weaker does not mean that you actually are. Expectations are orthogonal to actual power/skill/knowledge/etc.
There is a point to be made about choosing the correct strategy or tactic: for example, a less-skilled karateka could opt to just shoot the opponent and win the fight. It does not make them better at karate than the dead guy, though. We often have options such as that: programming is hard? Make your living doing something else. So on, but that is only a strategy for avoiding the things that we find difficult.