Basically a political answer that answers nothing.

It isn't performance compiling, as that is only surprising for those that never used 90's compiled languages like Modula-2, Object Pascal, Clipper and co.

It isn't performance of code execution, as even GCCGO could beat the reference implementation, unfortunately now stagnant since no one cares to update it beyond Go 1.18.

And to go back to the article, as pointed out there,

> The Go toolchain does not currently generate any AVX512 instructions.

Thus leaving performance on the table.