I'm wondering what the benefit is of opening these apps in full screen, without any browser capabilities? Why not just allow users the option to run any browser tab in full-screen, and separately allow adding web shortcuts in the home screen that open in browser.

These 'home screen web apps' will just complicate things for the average user, since now users will get a different UI depending on whether they are visiting the site from a browser, or using the same site from the home screen.