I'm not a technician. But i would say it's about having the ability in searching presets. And to be able to have more presets availble at a time. And to have a more flexible preset system. That's not compatible with the old system.
I don't think you can load more than 128 presets at a time in an old DAW preset system, unless it can load both all banks and presets at the same time so it's a 128x128 presets limitation. It's how MIDI from the early 1980's worked (when MIDI arrived).
If you read the article in the Cubase help link about the Program Selector, that i posted, then you'll see the lists is limited to 128 presets for a bank. It in a way work like Arturias Playlists feature.
I don't think you have any possibilities to for example search among all your Arturia presets, like you have with the new Arturia browser system.
But keep in mind, that DAWs have developed their own preset systems to.
Perhaps you can also save presets that include effects an more in your DAWs own system. But still you might not be able to search any of those presets either, unless your DAW have developed a search browser system to do that.
Also keep in mind, that the functions you ask for is in Arturias system, just like i wrote in my first answer in this thread.
Let me ask you: Does your waves plug-ins ever have more than 128 presets loaded in the selector at the same time, the way you ask about? If not, then what happens, if you try to load 129 or more presets at a time? If yes , then do you find it practical if you have many more presets, especially if you wan't to find a certain preset?