It is definitely not true. I am an international student and I got admission to Top20 univeristies with a GRE-Math score of 80%. If you are aiming higher though, maybe it would be better for you to have 85%+.
From my experience this year (with applications), universities want you to have also a very good TOEFL score, since they are going to offer you a TA position. Keep in mind though that the most important factor is strong LoRs.