RocksDB, as I understand it, is a pretty old piece of software, forked from a Google product, which was already a pretty old piece of software, all written in C++. Doesn't seem to have previously been written in Python, doesn't seem to have a team of non-C++ programmers who decided to just learn as they went, and so it's not clear what parallels you expect to draw.

Maybe they're doing a Rust rewrite too? I'd be interested to read about that.