Because the definition of soundness is that if a program typechecks it does not crash at runtime. This is a collection of unsound programs that syill typecheck.

Because the definition of soundness is that if a program typechecks it does not crash at runtime. This is a collection of unsound programs that syill typecheck. Since there is no difference in Python and other untyped languages between a potential typechecking stage and runtime the definition is meaningless for them.