No, Apple isn’t your guardian angel with the press of a button.

Apple does extensive audit of mobile apps, including limitations of tracking. So the app cannot spy on something you are not letting it to know. But you are giving it a bunch of info voluntarily.

I’d say using that app on iOS is similar to making a food delivery order using a loyalty member ID. Basically, you are letting the company (McDonald’s) know who you are, what is your phone number, where do you live, and what do you like to eat. And if they wish to, they could use all that to purchase your profile from a data brocker. Or they can sell that info for a few cents to make up on that discount.