SMT is like a shared kitchen. Even if you're unable to see the other person in it, if you go to use the sink, oven, or microwave and have to wait because it's in use, you know some small bit about the other occupant. Knowing how long you have to wait tells you more. Knowing what is already stocked in the fridge from the other occupant that you can immediately use tells you a lot.

Separate cores are more like completely separate kitchens. Sure, the grocery delivery service might take shorter or longer some times, but it's hard to tell much beyond general area business from that. What's in your fridge is what you put there.