This is not true, the way to avoid the friend zone it to make a declaration of intent early on. This takes balls though and men who try the "friend" routine often lack the balls to make that move so it becomes a self fulfilled prophecy. You don't have to be macho or a jerk you just have to be confident. Another good trick it to not put all your eggs in one basket. If you are a single guy you should be wooing multiple women at once until you find the one you like best, this way if any 1 rejects you you arent devistated, you have other options. Most women do this all the time, no reason men shouldnt eaither.
I find that men who go the "friend" routine are often more vile then men who are up front about how they feel. Befriending a woman just because you are sexually attracted to her is a false premise to be someones friend and its dishonest, which is why it often fails and the woman has to drop the guy when he starts getting pissed off that she doesnt realize that he is secretly in love with her. I mean... honestly...
There was a web comic one time I remember seeing, and its content was similar, it was a guy who tried to friend some girl, and she started dating what her referred to as "some jerk" which lead him to some tirade about how all women just want assholes and jerks. To which is friend replied, oh I see, he's the jerk because he had the balls to ask her out, and youre not the jerk because you tried to manipulate her from a secret agenda by becoming her friend and helping her do her homework etc etc etc.. it was pretty poingent.
If you like a girl, LET HER KNOW, dont try to befriend her with an agenda, you will rightfully fail!