PampiiiiThe following is my understanding but I’ve been wrong before.
Sold out - item was in stock (faster shipping) and all of them have been claimed. People can still cancel or adjust their orders, so it’s not perfect.
Sold through - the allotted time period to place an order in the group but has passed. Generally this is something that is going to be manufactured. So there are no limits on quantities.
Thinking about this a bit I suppose drop could mark an item as sold out and if enough people change their minds and cancel their orders, move it back to available..?