In iOS 12.0.1 on iPhone, what is the point of the block list? It doesn't block calls

I get spam calls on my iPhone SE. I have caller ID. I have a contact called "do not answer". The contact is blocked Inside the "do not answer" contact I keep a list of all the spam numbers that call me. In iOS 12.0.1 I get calls saying Incoming call from "do not answer". How is this possible? Doesn't the phone app see its showing the "do not answer" contact that should be blocked? The only workaround I have found is to set my "do not answer" contact to have a silent ringtone without vibration but it still interrupts use of my phone This has been ongoing since my iPhone 4s days