Calling the request currently doesn't give any indication if the OS supports the App Tracking Transparency at all.
This is in most cases not a problem as it would get called and move along, but a reasonable implementation approach would be to request tracking and then wait in a coroutine until a response is gotten in order to track opt-in rates etc.
On devices without support this would cause hanging behavior if no timeout is provided or have those on an unsupported version having to wait for a timeout.
All of this is possible to work around of course, but as the documentation for the package doesn't mention anything it would be expected to be handled under the hood.