Reproduce it
Fill an area with sensors, and another one with shriekers.
Execute the command in the next step.
/summon mob ~ ~ ~ {Silent:1}
❌ The bug reproduces
What I expected to happen
The shrieker to detect the mob when it's above it
What happened
The shrieker does not detect the mob.
Sculk Shriekers only react to players.
Sculk Shriekers and Sculk Sensors react to vibrations, not sounds. They're different game mechanics.