Sure we can all say "hello" but what happens after that? How can they follow up and make the woman in question not think that he's a creep?
Women think different than us, they're not males, buddies, dudes or bros so we can't talk to women like we do with them. The techniques he's referring to are not PUA and they are not 100% proof guaranteed, they are methods to establish a way to communicate to them.
A technique could be something you acquire that you don't normally have. Flirting is a technique if you need a detailed description of it just take look at this
page.
Also, why do you generalize? nobody is saying they're "putting the pussy on the pedestal" when they're saying they act different when they are with women than with men