Well, if you want to be pedantic, std::unordered_map first appears in the C++ working draft in 2006 (N2009), which is before Rust was first publicly announced.
I do want to be pedantic, but not in a fair way :)
The C++ 11 standard was not required to standardize broken garbage from many years ago.
WG21 pulled C++ 0x Concepts (a much more powerful feature than the "Concepts Lite" which landed in C++ 20) because they argued it might take too long to implement, ridiculous as that claim is, so there's no reason to keep something terrible just because it's in a draft paper.
