His complaint is that implementation details of the interpreter have leaked into the specification of the language, such as it exists. The result is that altern

His complaint is that implementation details of the interpreter have leaked into the specification of the language, such as it exists. The result is that alternate implementations have to mimic those quirks of the interpreter in order to achieve compatibility. Having an abstract specification of the language, rather than "whatever CPython does", would give implementors more freedom, and thus allow the use of Python in more places and circumstances.