The updated apps probably now provide the ability to detect phone numbers in the content shown in the app and allow you to make a phone call (or get to the dialer) from within the app.
With the Windows Phone being constantly updated, so are the developer tools pertaining to the OS. As the OS is updated, apps can start making use of the newer features available in the developer API's.
The apps you list are all Microsoft and Nokia apps and it makes sense that these apps are first to take advantage of any new features.
From the Windows Phone Dev Center:
Use the phone call task to enable users to make a phone call from your application. The phone call task launches the Phone application and displays the phone number and display name that you specify. The phone call is not placed until the user presses the call button. By using Launchers, you help provide a consistent user experience throughout the Windows Phone platform.