PopGeo: Output not a flat list

This is noob question about Grasshopper: Why does PopGeo output a list at path {0, 0, 0}? Why not a flat list?

(please correct terminology if wrong)

I think it just retains the input tree structure and adds a branch to it

specifically for {0;0;0} :

Thanks, although Grasshopper still reports 1 branches:

So each component extends the branch by 1. (just terminology)

This is good to be aware of. I guess I will use flatten more often in the future to avoid messy structures.