Do the nuts actually help the fermentation or are they just here for texture?

You don't need the nuts for fermentation! It's the lactic acid bacteria on the fruit that will make this happen.
I've found that oily things (nuts, avocados, etc) can be an added challenge in fermenting, because they oxidize and rise to the surface whether you want them to or not!
Good luck!

I'm sorry you haven't gotten an answer to your question yet. You could always try sending a message to WinnieAb too!