The wrapper (plugin API abstraction) is an AudioProcessorListener.
When a parameter is changed, the audioProcessorParameterChanged() callback is called and the wrapper communicates that to the host.
Same for updateHostDisplay() which calls audioProcessorChanged() with the appropriate ChangeDetails flags.
Try first if updateHostDisplay() works for you, it did for me, but I know there were reports that some hosts didn’t respond to updateHostDisplay(), so people added fake parameters to trigger the change.