When an item is dropped on the ground (including wool), the sculk sensor is able to detect the vibration.
MC-253938
Sculk Sensors can detect dropped items
Resolved
Works As Intended
1
The triaging of MC-252258 suggests that all items that come in contact with the ground should produce vibrations with the exclusion of wool and carpets. The behavior you described in this report is very likely to be working as intended.