Is there any link/documentation where its recommended to "remove the old ruleset / access group / applications ... etc from the HC, CS, and CSHC framework.". Are you facing any issue/impact due to old access group etc.
You may look for Designer Studio-->System-->Database-->Optimize Schema landing page to find and remove unused tables etc.
Yes you are right, the platform upgrade have steps such as Generate/Execute Ruleset CleanUp Script or Cleanup step but when we upgrade any pega strategic App or pega fraework it is more of importing product/application files/bundles so i don't think there is any such cleanup steps in case of framework upgrade.
For further information, you may raise a support ticket for additional guidance.