The irony is that I'm still technically correct, as literally every example (from C++, to C#, to Python, to JS) have been object property assignments abusing getters and setters—decidedly not variable assignments (except for the UB example).
That sounds like a recipe for having problems every time you encounter a nonstandard contract. Are you actually saying you willfully decide never to account for the possibility, or are you conflating "ought not to be" with "isn't"?
If I'm programming in a language that has the possibility of properties, it's absolutely a potential expectation at any time. Which is one reason I don't enjoy programming in such languages as much.
To give a comparable example: if I'm coding in C, "this function might actually be a macro" is always a possibility to be on guard against, if you do anything that could care about the difference (e.g. passing the function's name as a function pointer).
More commonly, if you look at things like c++'s unique_ptr, assignment will do a lot of things in the background in order to keep the unique_ptr properties consistent. Rust and other languages probably do similar things with certain types due to semantic guarantees.
Though Rust only cares about mutability, it doesn't track whether you are going to launch the nukes or format the hard disk.
Rust provides safeguards and helps you to enforce mutability and ownership at the language level, but how you leverage those safeguards is still up to you.
If you really want it you can still get Rust to mutate stuff when you call a non mutable function after all. Like you could kill someone with a paper straw
