> Owning references are a part of modern C++

Maybe we're thinking of different things, but I don't think C++ has owning references, modern or not? There's regular references (&) which are definitely not owning, and owning pointers (unique_ptr and friends), but neither of those quite match Rust's &.

Ah, okay, that is a good point. I was not aware of that subtle difference, and replaced "owning reference" with "owning pointer" in my mind.