Thanks for the feedback!
You're right, just listing features doesn't make the use cases very clear.
I'm planning to add more concrete, real-world examples to the README and examples to better show where wavelet matrices really shine.
No, the library itself does not use unsafe Rust at all.
The Python bindings are built using PyO3, which internally uses unsafe (as required to interface with the CPython C API), but that is fully encapsulated within PyO3. The core data structure and algorithms remain purely safe Rust.