Individual app settings persisting after reinstall?

When I am in the settings app and scroll the the bottom where I can see all the apps I have installed and choose one, there are several settings such as "Siri & Search" and also options like "Background App Refresh" and others depending on the app

After messing around with these preferences, I have noticed that even after uninstalling said app, and installing it again, these settings are still changed. Where are these preferences being saved, and how can I return them to their default? Somewhere within my phone these app preferences are being saved, with seemingly no way to revert to default.

I was under the impression that all app data is deleted when an app is uninstalled, however this seems incorrect as the preferences I change within the my iphones settings app are being remembered. I have turned off all icloud backups.