You're right, python3-setuptools is in bionic, I was looking at the setuptools source package which is not in bionic. python3-setuptools in bionic comes from the 'python-setuptools' source package instead.
In any event, this issue should not affect the python3-setuptools 39.0.1 shipped as part of the bionic release; it is only reported to affect setuptools 66.
You're right, python3-setuptools is in bionic, I was looking at the setuptools source package which is not in bionic. python3-setuptools in bionic comes from the 'python-setuptools' source package instead.
In any event, this issue should not affect the python3-setuptools 39.0.1 shipped as part of the bionic release; it is only reported to affect setuptools 66.