Waves tune doesn't really work in real time. It creates a second file with the pitch correction, and plays that back instead of the original file.
It's hard to clearly explain what it's doing. It does not process in real time, but it is not destructive. It creates a file and stores it someplace and plays that instead. That's what it is doing when you play the file through it so that it can read the notes.
In fact, if you try to edit the vocal track after you apply the tuning, you won't hear the edit. If you, for example, mute a word, when you play the song the word will still be there.
I'm beginning to think that my work around may be a good practice in most situations which is to take a close to if not in fact final vocal track, apply any needed pitch correction in a rough mix to be certain you can live with that aspect of it, Then remove all FX on the vocal track except pitch correction and render it to a new track. Now you've got your pitch corrected vocal track that you can do with whatever else you want. You can even mute a word or make other edits on that track and still have your pitch correction in tact and unaffected.