> I see optimizing away 'if __debug__: ...' clauses, when __debug__ is False (and 0) as currently documented language behavior, not a 'deep implementation detail'.
https://docs.python.org/3/reference/simple_stmts.html#the-assert-statement

I don't think you can conclude that is documented with this argument. What's documented is what happens with the assert statement, not with arbitrary dead code. The link between the two is at least an interpretation, not an explicitly documented think.