I’m not sure a single example of a C wrapper not idiomatically designed is a good example of the potential of a language. It’s like pointing to the source for any given STL implementation as quintessentially C++ coding style. RefCells tend to be considered an anti-pattern AFAIK since they leave invariant checking to run-time. It's meant as a hack/patch if you can't actually design it idiomatically for some reason, such as in this case, FFI to a C programming model.
I can point to other UI examples, like game engines written in pure Rust, using array indexes with clocks on access to invalidate possible use-after-free accesses with outdated indexes.
