Blocks doesnt keep the "CanPlaceOn" Tag after being Placed but they keep names and such...
The Shulker Box could be really usefull as a backpack in adventure maps.
but you can place them only once...
I know its maybe abit like a suggestion... but if the shulker box keeps the name... maybe its a glitch if it doesnt keep the tag! I dont know! but to be honest it doesnt really metters because its a thing that should be changed/fixed
Feature request, not a bug.
No block saves any tags but tags from the BlockEntityTag tag and the display name,and then again, only certain block entitys save the name.