It’s protocol to NOT allow EMTs to declare someone dead. An EMT (with a few hours of community college training, mind you) are not trained for advanced resuscitation that only doctors can perform. This absolutely will lead to excess mortality.
EMT-Bs aren't, but the BLS ambulances they staff shouldn't generally be assigned as the only responding unit for cardiac arrests, anyway. And given that, it's not clear why you think there will "absolutely" be excess mortality.