It would be good for Python to have more rigor in its definition. But the situation here doesn't have an analog in the Python world: there is no "PythonSpec" third-party test suite that is a) more complete than the official suite, b) exposing segfaults in previously working code, and c) going unused by the core developers.
https://bugs.ruby-lang.org/issues/7549#note-2
1. Matz is, and always will be BDFL. 2. The core Ruby team wants to talk in terms of C and MRI being the Ruby spec, not a third party/written RubySpec