When a wither shoots a wither skull, sculk sensors do not react, despite this being a projectile fired. According to the 20w49a changelog, this is a valid vibration.
- Build a bedrock box to contain the wither, in case something goes wrong:
- Go inside of the bedrock box, and summon a wither riding a minecart:
- Place a sculk sensor next to the wither
- Use a spawn egg to summon a chicken on the opposite side of the bedrock box
- Wait until the wither attacks the chicken by shooting wither skulls
Notice how the sculk sensor is not activated when the wither shoots its skulls