IsharaMeradin and Pevey, who discussed the change in this thread: https://forums.nexusmods.com/index.php?/topic/1170791-keep-npcs-from-picking-up-dropped-objects/
Vemonus from http://gaming.stackexchange.com/ for pointing me in the right direction.
Donation Points system
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This mod is a small tweak to the NPC AI packages which prevents NPCs from going after items you drop on the ground. It works by changing a couple of the AI packages so that they are given an activation condition which will never evaluate to true. Useful if you find this behavior annoying, or if any NPCs or followers you share a home with are interfering with decoration attempts.