It's extremely hard, so with 13 extra years they were able to make an astoundingly bad job?
It's hard to even believe this was trying to be general.
Notice that not only the hash tables themselves, but the infrastructure is garbage too. In 1998 C++ STL is one of the earliest generic programming APIs, nobody knows how you should implement the generality of something like hashing, fine.
But by 2011 people had tried several things, and this (the std::hash templated callable which returns a machine-word integer) is not even a reasonable attempt at a known good design.
It's hard to even believe this was trying to be general.
Notice that not only the hash tables themselves, but the infrastructure is garbage too. In 1998 C++ STL is one of the earliest generic programming APIs, nobody knows how you should implement the generality of something like hashing, fine.
But by 2011 people had tried several things, and this (the std::hash templated callable which returns a machine-word integer) is not even a reasonable attempt at a known good design.