We could possibly give the developer the benefit of the doubt that they're not doing anything inappropriate with the data but frankly why pass your data through a third party that's not part of the project.
And why install an app requiring access to your shared local storage? The GitHub repo claims the website an animations are slow which sounds like BS to me. It works fine on a five year old phone I use for submitting.
Just contribute here if you're so inclined, much more sensible:
Sure, you can get the source but as I said it's still a pointless step to go via a third party
And your point makes little sense, because if the site was not working how could the app get voice data into the project. I've had some involvement with these projects over the years so I'm not just firing off arm-chair comments on this. They wouldn't have been able to add this new voice data if the site was under developed as you imply.