Isn’t the standard form BuildRequires: %{python_module pyasyncore if %python-base > 3.11}? Let me try it.

Also, there is https://github.com/openSUSE/python-backports-generate/blob/master/get_all_specs.py which downloads all SPEC files from whole Factory (default, it could be any project in OBS or IBS) to the current directory. With that you can have a huge library of all possible tricks at your fingertips (or as input files for your grep).