Astro-turfing for what? I guess this falls into the "uneducated" category. From my apparently uneducated perspective, phones need to be a concern if you're worried about your voice and activities being recorded. Most users have no idea that, for example, Google Assistant is always listening on Pixel.

Siri is not enabled by default, they use a different approach to get users to opt in. Step 8: https://support.apple.com/en-us/HT202033 has a much bigger button to enable Siri, but users are given a choice and skipping Siri takes less time so it’s easier if you’re not going to use it.

Completely deactivate it

If you choose to disable Google Assistant completely, follow these steps:

    Open the Google app and select Menu (the three bars)
    go to Settings
    Google Assistant section click Settings > Phone and disable the Assistant option

I have a custom domain and disabled it for my family:

Switch off Google Assistant (for entire custom domain) Click Search and Assistant. Tip: Scroll to see all services. ... Control who uses Search and Assistant in your organization

    At the left, select the organizational unit.
    Select On or Off.
    To keep the service turned on or off even when the service is turned on or off for the parent organizational unit, click Override.