DoD does not say where it happens. 0...80 and 20...100 are both 80 % DoD, but with vastly accelerated degradation in the later case.

Low voltages are only associated with degradation when they are far below the cut off voltage, so <2.5 V here as well as for Li-ion and Li-Po. For Li-Po, which has arguably the least tolerance:

You can go down to 2 V and it will only damage the cell slightly(!) faster over the next 100 cycles of always going down to 2 V. All the batteries I ever had accidentally over-discharged recovered just fine. No increased leakage, no capacity loss.

Here an actual source, look at figure 7. Even down to 1.2 V the cells still reached 50 cycles until they were at 80 % remaining capacity.

I don't know where the misinformation comes from regarding "instand damage" below somewhere in-between 2.5 and 3 V. But I assume that, since the voltage drops very rapidly at that point, people actually ran the battery down into the ground, even reverse biasing (negative voltage) the most depleted cell(s), thus doing real damage. This should not be possible with a BMS.