When the first beta of iOS 10 was released it didn't take long before some web developers discovered that user-scalable=no stopped working on their websites. Soon issues started popping up at Stack Overflow and drama happened. Probably some developers are already working on their JS plugins to fix this and gain some extra stars on Github.
Before Universal Links the primary way to open up apps was by trying to redirect to the app's URI scheme, putting the routing logic in Safari. There was no way to check wether the app was installed or not. Meaning developers would try to open the app using the URI schemes 100% of the time in the off chance the app was not installed and using a timer to fallback to the App Store page.