A comment I posted today on the German forum talking about replacement packs.
Akku nun getauscht ehem. / Soul 2015 lädt bis 94% nach BMS Update / Antrag Akkutausch
Screenshot taken today from [url=https://www.kiapartsnow.com/parts-list/2016-kia-soul_ev/engine_drive_motor/high_voltage_battery_system.html
The interesting aside that I take from this is that the SK Innovation E375 cells for the original soul EV were in production from July 2014 to May 2016.
The newer E400 cells for the MY2018 Soul EV began production exactly a year before that car was released. There must have been a considerable stock of the older cells when the changeover occurred. But given that the original cells are no longer produced and presumably no longer in stock replacement battery packs must now use the newer cells. A possible exception to this is the refurbished packs seen in the US. Theoretically they could get the older cells that are in good condition from crashed cars, or from cars that had a replacement battery but only a single cell was bad. I am guessing this has happened based on the fact that my replacement pack is obviously better than the original and yet many US posts have commented that the new battery does not seem to be so good. The part number for those packs is 37510 E4200R REMAN PACK ASSY-BATT.