I have auto-renewable subscriptions in my app. These subscriptions come with 3-7 days trial (money charged only after this trial period). I didn't place any custom code for event tracking in source files, and facebook tracks all of these events just fine, except purchases. I thought that was because I've never had purchase events untill today, but today somebody subscribed, and "purchase" event still not tracked. Instead "Initiated checkout" event was tracked with value = subscription price.
Question is why it is not tracked? I am planning to create an advertising campaign with purchase events optimization in facebook, but if they are not recognized, then I can't do it.