Li-ion battery cell balancing statistically unnecessary when many cells are in parallel?
Your title mentions cells in parallel yet the text talks about cells in series, that's confusing. I just answer both cases:

In case you mean cells in parallel:

No, cell balancing does not work like that. What matters is the difference in voltage between individual cells.

Using a large number of cells does not guarantee that the cell with the lowest voltage will have a higher voltage, closer to the average. So when that cell is connected it will still be charged (with a large, possibly damaging current) by the other cells.

Any time two (or more) cells are about to be connected in parallel their voltage must be similar to prevent large current to flow. This is done by balancing. This applies to any number of cells.

In case you mean cells in series:

No, cell balancing does not work like that. What matters is the difference in capacitance of the individual cells.

When one cell is almost empty but the other cells are not then you cannot keep using the battery pack as that empty cell will then be reverse charged and it will be damaged forever. So discharging has to stop.

The same is true for charging, when one of the cells in the series is nearly full the charging current through it has to be lowered to not overcharge it.

Using a large number of cells does not guarantee that the cell with the lowest capacity will not be over charged/discharged.

Any time two (or more) cells are about to be connected in series the voltages of all cells need to be monitored to prevent over charging/discharging.