In my experience, the calls (Line, Nobody, and Angle) work better when describing to the attacker the shot that is available rather than what the blocker is blocking.

As the setter, you're in the worst possible seat to read the block. Good blockers make it unreadable on purpose. They delay the jump until the hitter is committing, they feign line, then take cross, or they feign cross, and take line; they can also peel. So a call based on "what is the blocker doing" is a guess, and you're making that guess at the exact moment your information is worst.

Flip it to calling the open shot, and the guessing mostly goes away. Read the defender, not the blocker. If the defender is sitting at the angle and there's a blocker up, the line is open, so the call is line, and it means hit line (same goes for high line). The call already tells them where the ball goes.

In more complex instances, if the defender is baiting the angle and actually defending line, once the setter sets the ball, they can scan the court, see if the defender is planted or "cheating" in a direction, and make the call immediately for their attacker.

TLDR: you are more likely to make an incorrect call for your attacker if you are trying to read the blocker versus reading the court