The Sonic attack should be able to just go through shields like it does blocks. This makes the new attack really easy to cheese. This is also inconsistent with guardian beam attacks.
MC-250171
Warden Sonic Boom attack can be completely mitigated by shields
Resolved
Fixed
11
(Unassigned)
Confirmed
Important
Mob behaviour
warden, warden-sonic-boom
22w15a, 22w16b
22w17a
Retrieved
Reasoning onto why this might be a bug is due to the fact that there are types of non-physical damage that shields can't block, such as guardian beams. Whether or not sonic boom attacks are considered physical damage is up to the devs, but it might be inconsistent with how it is able to penetrate walls.
Just saying it's "cheesable" isn't enough reason to call it a bug.