The point still stands. If you hold an index into an array of widgets, and the widget you reference is removed or replaced in the array, you could get behaviours 1, 2 or 4 depending on your implementation. Rust's index-into-array pattern removes the possibility of memory leaks, but it also removes most of the benefit of having a borrow checker in the first place.

Its basically a less performant, less ergonomic version of using raw C pointers. Less ergonomic because you need to write your own allocator for your array. And its less performant because fetching the associated struct from memory requires 2 fetches rather than 1. If you're convinced dynamic memory management is the only solution to your data structure, rust's unsafe{} seems a better choice. Its in the language for a reason.