Hello @Geez ,
here is something I have been observing with the Loot Table for quite a long time now and you should be able to REPRODUCE/observe it as well.
It becomes especially apparent when you are loot-cycling. When you see a specific item spawn, for some odd reason, the exact same item will spawn with a high chance in the surrounding buildings (entire loot zone/town).
Lately I lootcycled small sheds and garages in a small town, in order to find a spark plug. When I finally found one after about 30 minutes, suddenly in the next shed there was another one, and I found two more looting the rest of the sheds whereas before there wasn't a single one during the 30-45 minutes of lootcycling.
I've also observed this swarm spawning WITHOUT lootcycling.
EDIT #1: The phenomenon can be observed on official vanilla servers.