Explorer does actually use Rust (and polars) for a lot of its work -- its one on the libraries I looked at while figuring out my memory management issues.
No, it doesn't -- looking at the website that's an explicit trade-off of pure performance vs 'Elixir-ish-ness'. It would certainly break a lot of expectations to have data mutating like that without it being hidden away somewhere, so I can understand why they went that way.
In my case the data I'm dealing with is more of a store than a single data item, so I'm leaning on the example of things like ETS. Also it's within a single application rather than being a large generally-available library, so the trade-offs are different. It would be interesting to know if they did tests though.