Facebook’s big ad business on mobile is advertising to install apps. That’s also Apple’s ad business on mobile (ads shown on Apple News, and in the App Store itself). For Facebook to show attribution of ad conversions, they must do tracking “across apps” (from their app where the ad was clicked, to the advertiser’s app). For Apple to do the same attribution, they can call it “interactions with Apple services”, because the purchase is done through the App Store. In that sense, both are going after the same user actions but different language can be used to describe them.