Related:

    Settings -> Siri -> Apps (Siri app access) -> [an app] -> Learn from this app

This is on by default for all apps and it “Allows Siri to learn from how you use [an app] to make suggestions across apps”. I found no global setting for all apps.

More details: https://support.apple.com/en-mn/guide/iphone/iph6f94af287/io...