Using shields triggers sculk sensors

I was in the deep dark biome with my shield in my offhand when I accidentally right clicked holding nothing on my primary hand, causing my character to perform the blocking animation. To my surprise, it triggered a nearby sculk sensor, which in turn triggered the sculk shrieker next to it.  Letting go of right click triggered the sculk sensor again. The shield blocking animation is silent (when not being hit by melee attacks or arrows), so why does this trigger the sculk sensor?