You might be reading about 2 different Voltages.

1) Voltage under load. While running, the Voltage is pulled down under the load of the motor. The lowest anyone recommends is 3V per cell. Like several others have mentioned I also prefer to use a slightly higher cutoff in the 3.2-3.4V range and rarely even hit it. And have great pack life with no noticeable puffing.

2) Resting Voltage. After the pack has sat for awhile. The Voltage will recover or bounce back up a bit. Usually back up to near 3.7V per cell. There isn't much capacity/run time left below that resting Voltage.

A typical resting Voltage vs capacity table for a lipo cell discharged to 3V/cell cutoff (under load):

4.20v = 100%
4.03v = 76%
3.86v = 52%
3.83v = 42%
3.79v = 30%
3.70v = 11%
3.6?v = 0%

Most recommend limiting discharge to about 80% (20% left) for best lipo life.