Apple Configurator MDM profiles can control Siri behavior, e.g.

https://github.com/jankais3r/Siri-NoLoggingPLS

  Disable server-side logging of Siri requests for your Mac, iPhone and iPad

You can disable Siri (and Apple Intelligence) entirely via Apple Configurator or asking the nearest LLM for .mobileconfig file with:

  <key>allowAssistant</key><false/>