Mining a chest allows players to pick it up with all the items inside and carry it in their inventory. Also supports vehicles, tanks, and accumulators.
Mods introducing new content into the game.
More than just chests.
Blueprints should not contain packed entities. at least not if packing is switched off. https://prnt.sc/FWUO3K4LFhfq
on the other hand, if i cut out a packed box (temporary blueprint), it will not be pasted, even though it is in the inventory.
and third, sometimes buildings come packed into the inventory (e.g. transport drones request depot) but if placed back, the content ist lost.