Yep, normal. The wording is often confusing as some websites refer to the VOD track (Incorrectly) as a track that is NOT sent to Twitch.
Although I haven't updated to use enhanced broadcasting as yet...I'd presume it still works the same way.
The best way to think about it is like this:
Twitch VOD track = Well, it's your VOD. Which is something you want people to see and hear.
If your Twitch VOD track = 2. Any sources that have track 2 selected will be in your VOD. If you uncheck track 2 for any audio source, it won't be in the VOD.
Just have to be sure that you don't have the default desktop output playing anything you want muted, always add a music source via adding a new input.