The Bug:

Sculk sensors are not activated upon loading a crossbow.

Steps to Reproduce:

• Load a crossbow.
  →  Notice how the sculk sensor does not activate upon doing this.

Additional Information:

This same idea also applies to crossbow-wielding pillagers. 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 loading a crossbow.