You see econ predocs getting A’s in real analysis, then retaking the Math GRE multiple times for basically middle school math because the rumor is that top PhD programs automatically filter you out below a threshold, which means getting one question wrong
If you get 100% on the Math GRE, you're at the 91st percentile.
The test measures grind and attention, not capability. It tests whether you can go 2 hours with no slipups.
It's interesting that grad programs don't want to know the full ability distribution of their applicants.