These calls aren’t necessarily rare, but they aren’t routine if that makes sense.

Avoiding miscommunications and de-escalating tensions is the entire point of these lines.

I remember reading a story about US military leadership contemplating striking a target in Syria a while back. Russians (mercenaries or regular armed forces) were suspected to be operating in the area, but their generals denied presence on this emergency line, so the US bombed away. Russians ended up among the dead, but their leadership denied sponsorship, so this wasn’t necessarily a “US targets and bombs Russians” event which could lead to general warfare.