May relate to MC-164184.
The bug
If the loot table for shulker boxes is changed such that they drop a block that is not a shulker box, they will correctly drop that block if broken in Survival mode, but not when broken in Creative mode.
How to reproduce
A data pack that makes default shulker boxes drop chests is attached to this ticket.
Download and apply the attached data pack
Place an item in a shulker box
Break the shulker box in Creative
Break the shulker box in Survival
Expected results
In both cases, a chest would be dropped.
Actual results
In Creative mode, a shulker box is dropped instead.
Can confirm.