This box also fits a 12S 6A charger, so when it is charging you remove the series connector(short!) and you can charge the two 12S packs in parallel. in order to not disconnect them in series you would need a 24S charger like for an EUC.
Ideally it would have two+ different cccv outputs but with just one it is still possible to charge more than one board as once as long as they are all close enough in charge. There is some math so that could be determined.