I believe the intention is to allow operations on multilayered business objects to be composable. So your approvalConfirmationUpdated() method may actually be made up of a sequence of smaller operations, each of which I might want to use elsewhere in the application. Lenses allow this to happen succinctly, and works better with eg the Java streams API.
I got that, my point is that such composability is rarely better than good old OOP with encapsulation. Enumerating all possible state transitions on object interface leads to better design than procedural programming (and composable operations are procedural programming).
