Warden's sonic boom attack doesn't work when 16 blocks away horizontinally

A Warden's sonic boom attack is meant to not work when the target is 21 blocks away, but instead the sonic boom stops when 16 blocks away.

How to reproduce:
1. grab green concrete, orange concrete, red concrete, and a sign.
2. put 21 green concrete on the floor, put an orange concrete on the 21st block and a red concrete on the 16th block
3. put the signs down every 5 blocks until 20 blocks and trap a warden in a box in block 0(warden not on the line)
4. anger the warden and observe what happens.

Observed Results:
The Warden's sonic boom can't reach you when you go on block 16

Expected Results:
The Warden's sonic boom should hit you past block 16.