What stops is the telling. No email when a certificate starts running out, none when the record that renews it quietly disappears, none when your CNAME gets deleted. The checks keep running and the dashboard still opens. You just have to be the one who goes and reads it.
What does not happen is us pulling your website off the shield that afternoon. Your domain points at us, so taking you off is an action that can break a site which was working, and that is exactly why it is slow and loud on our side: you get told, more than once, with the steps to point your DNS back at your own server, before anything moves.
The way out entirely is that one DNS record pointed back at your own server. Every screen that has a website on it tells you that, instead of leaving it for you to find in here. The step by step version is written down, and those screens link straight to it.