There are many ways to install assets with a policy. A package installer (.pkg), a Jamf package, (which can be a .dmg or .pkg) a script, a combination of these, multiples of all of the above, etc.
The 1st thing you should check out is the Jamf documentation on packages:
https://docs.jamf.com/10.42.0/jamf-pro/documentation/Package_Management.html?hl=uninstall#ID-000207e...
However, I indeed think maybe you are missing something because there is no magic button for uninstall. If following the Jamf docs doesn't help, you need to do some more digging.
3rd party vendors sometimes provide their own unstall script or app (Adobe often includes "uninstaller" packages with their apps, e.g.)
You can track the .bom inside of an installer .pkg & use that to delete items at the paths where they were installed. You can create your own custom removal scripts, but, there are all sorts of potential issues with doing that depending on what was installed & how (sometimes, items installed may be signed & installed in a keychain, e.g., & these items may require being unsigned for removal) which is why there is no easy button for doing this...
So, look at the application or assets you've installed & see if there is an included uninstaller. If not, you should check the documentation for how to cleanly remove it. Once you understand that state, you can potentially make your own uninstaller or if the install is simple & you are indexing packages your may be able to uninstall simply.
