Working off of this thread to make sure it's the same building, look at the google maps here of the alleyway in the rear street. There's three things that would make this a perfect location:

1) Long alleyway with lots of gates and dead-ends. Why is this good? Controls the main entry and exit points and makes it harder to be ambushed. You can see the people and vehicles coming from far away. Plus, spotters can easily look over the area and signal if there's trouble, like potentially these two people hanging out by the playground down the alley, looking towards the building.

https://i.imgtc.com/aeCf0GP.png

2) The bars on the windows make that room a perfect spot to be a holding cell for humans. I'm not sure what the rusty thing on the door is, if it's some kind of viewport or marking, or just something glued on there.

https://i.imgtc.com/VQOndUI.png

3) Shipping docks allow workers to roll up the door, back up a truck partly into the garage, and empty the contents of the truck without people seeing what's coming out of the truck unless they were right there watching. https://i.imgtc.com/6HscnBP.png

4) Leftover glue on the middle door meaning something was glued on there, maybe one of those rusty things. Also a marking that says what I read to be "Chet".

https://i.imgtc.com/bAEm5Aw.png

Strategically this would be a decent location to hold people until buyers show up to get them or they are moved to another location.