I'm pretty sure that HHs/HLs doesn't make up the entirety of anyone's strategy. My assumption is that's just one rule of many that he uses to give him an underlying bias, filter potential setups and increase his probability of a successful trade. Might even be based on his own experience rather than rigorous stats.
Just one random analogy:
“The 10 day exponential moving average (EMA) is my favorite indicator to determine the major trend. I call this “red light, green light” because it is imperative in trading to remain on the correct side of a moving average to give yourself the best probability of success. When you are trading above the 10 day, you have the green light, the market is in positive mode and you should be thinking buy. Conversely, trading below the average is a red light. The market is in a negative mode and you should be thinking sell.” – Marty Schwartz
Think we'd all safely assume that Schwart's strategy didn't consist solely of buying a stock as soon as it got above the 10dema, and selling when it went below.
Or am I misunderstanding your argument?