You're thinking about security, and this enhancement is about integrity. The idea is simply that some third-level dependency won't be able to make global change

You're thinking about security, and this enhancement is about integrity. The idea is simply that some third-level dependency won't be able to make global changes to the program -- like making it non-portable (i.e. not allowing the upgrade of the JDK) -- without the application knowing about it. This is a brand new functionality that solves the problem that led to the 8 -> 9+ migration pain (and I hope you'll agree that was a relatively big problem). Integrity is also a prerequisite to writing any security mechanism in any layer of the code that is less prone to accidental vulnerabilities in a third-level dependency, and it's also a prerequisite to performance optimisations. For example, if Java strings were immutable, the compiler would be able to optimise some operations on them. Except it can't because even thought they're almost always immutable, some third-level dependency may decide to mutate one string in the program, and because of that the compiler can't optimise any. Such new and powerful functionality is indeed disruptive (in a good way), and all it demands is that libraries that need to, say, mutate Java strings or final fields let the application know so it could add a flag (if it's willing to take the portability/performance/security risks involved). That's it.