It is interesting - and fun! The term refers to people who are clearing stuff out, either bc they aren’t using it, they are moving, they need the cash, they are becoming minimalist, etc.
If you are on FB, you can find entire groups and pages dedicated to soap supply destashes. I have a friend who watches out for FB destash posts for me. And of course, you can search the general “for sale” posts on FB Marketplace, Craigslist, NextDoor.com, BuyNothing, etc. Search for “soapmaking supplies” and voila! I often see cutters, molds, supplies, FOs, etc.