The Bug:

Sculk sensors are not activated upon opening a hopper.

Steps to Reproduce:

• Open a minecart with hopper.
  →  The sculk sensor activates.
• Open a hopper.
  →  The sculk sensor does not activate.

Additional Information:

Quote from the 20w49a Changelog, "A vibration is anything that causes physical motion". I would definitely consider this as physical motion, as you are physically opening up a hopper. If opening a hopper in a minecart produces a vibration, why shouldn't a normal hopper do so as well?