that's true about cut-offs, but when it comes to comparing two absolutely matching candidates against each other - GRE, Ibt-Toefl, Acads + research/work experience - percentiles could be well gamed. The candidates with higher percentile scales will be favored by AdComs over those with lower percentile ones.
Some more facts: In 2011 according to ETS data the GRE General test takers' pool reached 800,000 people. Say roughly 15% people score at high percentiles either in quant or verbal or the combined (85% ranking, Q 162 or V 161, or combined). It makes the competition amongst some 120,000 people intense for some 22,500 places (rated schools 1-100) for each cohort accordingly - Masters and PhDs. Of course those competing for Masters will face more intense competition, because not every one looks after PhDs. Again this will be off-set by the number of places for Masters and PhDs available, since the latter would require a university funding and would be limited. Thus, 5 people per 1 admission place of course after all other criteria will be met, i.e. GRE, Acads and research/work experience