To get rid of the loopholes, Apple has provided an official way to integrate Siri with ChatGPT.

Head over to theSettings/System prefs app > Screen Time >turn it on and customize it to your liking.

For added security, check that to set up the Screen Time Passcode as well.

Content and privacy restrictions on Mac

Block ChatGPT Siri extension on iPhone and iPad

Choose Content and privacy on Mac

Choose Intelligence and Siri on Mac

Disallow ChatGPT siri extension on Mac