Some packages can build without python-setuptools and thus do not depend on it.
In this case /usr/lib/rpm/pythondistdeps.py fails in rpm packaging phase:

[   17s] Traceback (most recent call last):
[   17s]   File "/usr/lib/rpm/pythondistdeps.py", line 105, in <module>
[   17s]     from pkg_resources import Distribution, FileMetadata,
PathMetadata, Requirement
[   17s] ModuleNotFoundError: No module named 'pkg_resources'

But rpm-build-python depending on python-setuptools is not possible, because
that would create a dependency loop with setuptools and its build dependencies
(python-ordered-set)