Projectiles that can't be picked up when shot by entities can be picked up after being redirected by a Player. For example, this applies to arrows shot by skeletons and tridents thrown by drowned.
To reproduce
Requires the attached data pack (
[media]).
Summon a skeleton and have it attack you
Deflect an arrow shot by the skeleton in Survival mode
Walk to it to pick it up
Expected behaviour
You cannot pick up the arrow, since it has been shot by a skeleton
Observed behaviour
The arrow is picked up and is added to the player's inventory.
I've split this bug report into the two cases – MC-270910 is now about the fishing bobber issue.
The bug here is not that the owner changes (otherwise things like the "Return to Sender" advancement would break); it's that redirecting some specific projectiles causes unexpected behaviour due to redirecting changing the owner. That unexpected behaviour is the issue, not the owner changing.