CPython in particular exposes so much detail about its internal implementation that other implementations essentially have to choose between compatibility and p

CPython in particular exposes so much detail about its internal implementation that other implementations essentially have to choose between compatibility and performance. Contrast this with, say, JavaScript, which is implemented according to a language standard and which, despite the many issues with the language, is still implemented by three distinct groups, all reasonably performant, yet all by and large compatible.