As said by @cwalcott should works for apps that support deeplinking so apps that enable "tel://", "skype://" etc... However if you have an app like Tinder that as no scheme (AFAIK) shouldn't be detected. Indeed is still bad that they do that but seems they're basically using an "hack".
iHasApp has a large list of URL schemes, mapped to the
iOS App that they identify. The framework essentially
runs through all of these schemes, and determines which
URL schemes are handled by the current device, and create
a list of application ids as a result of successful
queries.
I was assuming there should be some sort of buffer Apple could have built in, but I guess being able to tell whether or not the user has left the app directly after hitting a deeplink seems difficult to deny… despite being hacky.
You are not correct. Each app that uses Facebook login MUST declare custom URL so that you can come back to it when you are transferred to FB app (it has a syntax "fb...", where "..." are replaced with FB app id). So you can assume that each and every application that uses FB login has custom URL.
Now Tinder declares 3 custom URLs actually: "tinder", "fb464891386855067", "tinderdebug".
