Try this:
Select a third-party plugin, NOT the M1 that you’ve chosen (the Korg collection’s devs did a good job), because this one handles the program changes and binds them to vstPresets. Select another one, so that in the inspector you can see this:
Now, you’ll notice that the shortcuts of previous/next, change the programs in the inspector.
You’ll also notice that there is no change to the selected preset of the VST.
This is because, when in the project window, Cubase uses these shortcuts to change program.
Now, if you open this VST and create some vstPreset files, you’ll notice that inside the browser, the previous/next shortcuts will change vstPresets.
This is how Steinberg decided to implement the previous/next preset commands. It is up to the VST to handle the program changes, and unfortunately not all of them do. This is why I initially commented that a program is not a vstPreset. Furthermore, note that you can create your own vstPresets, and then again, these will not appear in the inspector’s view which will continue to show whichever preset the VST attaches to the selected program.
Have a look here, if interested, the VST3 SDK supports program changes, but many VST makers simply do not implement this: