it works because links are defined in the hypertext and discovered by clients (say by the browser when a page is visited), so are new functionalities. A (well designed) web app is always up to date. In an Android native app the API URL(s) are (99%) hardcoded using the knowledge about the API of a certain moment. This auto-discovery mechanism works also for a spider.
Auto discovery does not mean that links are understood (@rel may help but..) you may need a human to decide but..
Suppose a (rest) application that lists links to its "services" in home page with the "service" page describing the service following a certain standard. You may have a bot that checks periodically the application for services you are interested in and be notified if a new service is available, with the possibility to navigate to the page and possibly subscribe.
Auto discovery does not mean that links are understood (@rel may help but..) you may need a human to decide but..
Suppose a (rest) application that lists links to its "services" in home page with the "service" page describing the service following a certain standard. You may have a bot that checks periodically the application for services you are interested in and be notified if a new service is available, with the possibility to navigate to the page and possibly subscribe.