You have to show a screenshot of what you have done. Your problem is because you are doing something wrong. For us to see what have you done wrong, we need a screenshot. Regarding triggers might also help, for instance maybe you made a trigger to research certain technology hence why the game "ignores" the requirements, because they are fulfilled.
BTW, he was pretty clear guys, there is an ability (default ability) called "Chage gold and lumber", he meant to add a requirement for use and he says that despite the fact that he added the requirement under Techtree - Requirements (in object editor), ingame the requirements are ignored.