The idea that this is something an app on a phone is responsible for is utterly terrifying to me. This should be handled by the OS, and completely isolated from apps so they can’t interfere or provide broken implementations.

The point is that Teams needs to handle emergency calling. What if someone uses a tablet as their phone? The OS can't always provide emergency calling capabilities. A tablet does not present itself as a phone by default, which is why it doesn't usually have a dialler. But if you install Teams or some other calling app, bam, it becomes a phone and needs to follow the law, and if someone opens the Teams app directly and dials 911, it still needs to connect.

Maybe emergency calls from the OS dialler should only be allowed to be handled by the OS, but is it as cut-and-dry as it looks? Not always.

Why does Teams need to handle emergency calling? What is the mandate that says it does?

I believe it is called Kari's Law. Anything that presents as a phone needs to be able to handle emergency calls, or something to that effect.

Edit: I'm not super familar with it, it's just something I remember reading before. It might not be Kari's Law exactly, as that seems to be more for Multiline Telephone Systems, such as in hotels or offices. Maybe I'm totally wrong and calling apps like Teams don't need to handle emergency calls and they simply choose to, but I'm pretty sure they are required to.

Wouldn’t it be better for apps on mainstream OSes to be both able and required to use OS facilities for that? I mean, it’s not as if Android doesn’t have a solution for this. Why should Android apps have to (redundantly and almost certainly incorrectly) implement this when the OS already does? Yeah a tablet isn’t a phone. But it’s running a phone OS.

I don't know, maybe your right, but should tablet makers be required to add VoIP calling capability strictly for emergency calls? All this is hypothetical, because I have no idea what I'm talking about and it's 2am here lol

If Teams has the capability, so does the tablet right? If it’s running Android, it’s already built for them. But more importantly, if it’s running Android I think this should be Google’s responsibility, not the manufacturer.

Edit: I’m sincerely not trying to come across combative and I appreciate you engaging this. If I’m frank it’s only because I’m trying to make my assumptions and expectations of the OS vendor clear