Also, in process manufacturing you may have by- and co-products; unfinished yield that may be re-introduced into the process. And you often can't predict what exactly comes out of the process. So you have to work with ranges (of specifications) and chemical formulas. All of that is provided with recipes and process orders in PP-PI.
As "lean manufacturing" came primarily from the automotive industry, process manufacturers always asked the question if they can reduce waste as well. Why not? You can not introduce 'one piece flow' but that's not the only lean principle. Why not heijunka level a production program or make every product every interval (EPEI)?
Peter L. King has written a book, Lean for the Process Industries. Dealing with Complexity, which beautifully translates all the 'automotive lean principles' to process manufacturing.
One of the most interesting ideas is the 'product wheel'. It represents the heijunka for processed products.
The moral of the story (if there is one) in either case is that there are possibilities with no end in the SAP system. Learn about them! Make them your own! Use them to advance your company's operations! And what is really exviting is that all this stuff works!