It is actually quite common. Lower ranked schools , a lot of the times, screen students purely on numbers. Your application may not get reviewed beyond the GRE scores in some cases and if you get lucky may be your GPA maybe looked at. With high ranked schools, they may be willing to take the risk in students even if their GRE or GPA lower than their average applicants as long as they deem the students will excel in their program. Do bear in mind, this isn't a standard operating procedure for all high ranked or low ranked schools.