Google should have built in some mechanism which verifies that the integration from Teams can't prevent calling 911 - either as part of Play Store verification, or as a general test of their system (they delegate to other apps, if these fail or hang the native mechanism should take over).
Having something that can screen calls for spam, something that can stop you accidentally dialling a premium rate number and getting an unexpected large bill, or something that can intercept a call and route it over a cheaper VoiP connection is really useful.
It needs to be a carefully managed feature, but it's certainly not "zero need".
911/112/etc. calls should just not be screenable or blockable by apps or susceptible to third party app crashes. They should be short-circuited to just happen on the default phone app, with little possibility for any interference from apps on the system.
