Unfortunately it has to do with planning. I'd have to do some research but I think it has to do with MRP planning and planning fences, it might be in the availability checking rule? But basically SAP allows the concept that any batch of zero quantity can be made again beyond the replenishment lead time. Which is pretty much a fallacy since by definition a batch should be unique.
But the one case I can think of is bulk repacks. You have a bulk material in a tank of say 10,000 gallons. The tank is sealed and used until empty. You packed out four drums from it into a new material number but you carry over the batch number from the tank. A very common practice. You sell the 4 drums to a customer. Your inventory of the drum material is zero. The same customer calls back a week later and says I want 8 drums of that same batch. You create a process order to drum out 8 more drums from that same tank. You can basically do this until the tank is empty. Thus "re-making" the drum batch over and over.
So SAP allows you to plan as if you can recreate the same batch over and over. Which in the above example, you can. (At least until the tank is empty!)
I believe it might be controllable but I'd have to research it some and i might not have much time this week to do so. Maybe you can find some more info on it though.
Glad you found the OSS notes!!
Ff