I've noticed fairly recently that certain websites on iOS seem to get a more persistent smart banner from Apple. For example on twitter.com and facebook.com I see smart banners like this:
Note how the smart banner doesn't have the usual close cross on the left (and it's slightly shorter than the normal one).
I've looked at the page code and neither twitter or facebook have the meta tag with their app-id linked.
So my question is how did they get these banners? Is this just something Apple has decided to add on their behalf due to the popularity of their sites / apps? Or is there some secret config you can add to a site to get these special banners?
Smart App Banners are dynamic. They are different depending on whether you already have the app installed or not. If the app is not installed yet, the big banner with the close button is displayed. If the app is already installed, the banner from your screenshot will be displayed.
You can find a detailed description about that on the Apple Developer Documentation.