Slight mismatches in capacity can be OK in series too, as long as you have a BMS watching the cell voltages to make sure none get too low when discharging and none get too high when charging. The risk is that the lower capacity cells get too low or too high while the overall pack voltage seems fine, causing dendrites to form inside those cells, leading to a short and a scary fire. It really comes down to how well the BMS is designed / programmed and how much you want to trust it.

Most people aren't aware of how dangerous it is to try to "revive" a cell that got too low so this technology definitely comes with significant risks for user error.