fgrieu:
Seems not unreasonable to me. Deep discharge of a cell is known to have the potential to leave it in a state of high internal resistance, where current flowing thanks to either the other cells supplying power, or a recharge attempt, will generate a lot of heat in the cell, causing the effect described.
My reading of the Boeing description is rather that "deep discharge event" is a carefully phrased reference to what may have been an internal short circuit. This both reduces the cell voltage and increases the cell's resistance to externally driven current, but only after the real damage has been done by the dissipation of the cell's energy inside the sealed case. That is what led to the venting they refer to, not current being forced through a benignly discharged cell.