You are quite right. The Internet is full of "stock experts" and their theories. It's not difficult to find a day where anything can happen in the MM's world.
Stocks were moving higher and then back down long before someone decided to present their "proven program" and call it a "Gap." There are very good statistical analysis programs for companies that have a strong history -- the GAP Theory is not one of them.
However, some GAP experts will continue to tout their "systems" and show it worked one day. Very good, a stock went up and it came down. Great theory.
Fools and their money....
John