I wish it were more clear what exact info we were giving to the app (not just generic "contacts" or "photos") and when the app is receiving that info. I know m

I wish it were more clear what exact info we were giving to the app (not just generic "contacts" or "photos") and when the app is receiving that info. I know more about coding than 95% of my friends and I still don't fully understand the depth of info that I transmit to an app when I agree to give it permissions on my iOS device. E.g., if I give Whatsapp access to my photos on my iPhone, does that mean all of the photos that are stored on my iPhone, including screenshots and hidden photos, are uploaded to Whatsapp servers? Does it upload when I take a new photo or when I open the Whatsapp app? So if, in this case, Whatsapp is indeed pulling all of a user's photos, including hidden photos, to their servers, I imagine many people would not want that to happen. So 1) I'd want to know ahead of time exactly what will be pulled and 2) ideally, I could have a way to use the app without giving it the keys to everything.