Note that the point of [static N] and [N] is to enforce type safety for "internal code". Any external ABI facing code should not use it and arguably there should be a lint/warning for its usage across an untrusted interface.

Inside of a project that's all compiled together however it tends to work as expected. It's just that you must make sure your nullable pointers are being checked (which of course one can enforce with annotations in C).

TLDR: Explicit non-null pointers work just fine but you shouldn't be using them on external interfaces and if you are using them in general you should be annotating and/or explicitly checking your nullable pointers as soon as they cross your external interfaces.