Generally, secure bits aren't set unless you explicitly set them. In order for the interpreter to even deny anything you have to run it with the secure bit set. In other words, something like this to ensure that python can only run some-script.py and that whatever that script calls can't spawn an interactive python (or even bash) shell: setpriv --exec-deny-interactive python3 some-script.py

So your point is moot because you wouldn't run cat some-script.py | setpriv --exec-deny-interactive python3

But instead, what someone might do is build a docker container where the entrypoint is setpriv and the command is python3 some-script.py, to ensure that their python web application can run inside the container but no bugs that might allow ACE to get an interactive shell will be exploitable because the interpreter inside the docker container will always have the secure bits set.