GH + Python - GUID manipulation

Hi,

I'm trying to manipulate grasshopper selected objects with a Python script,

1.For illustration purpose, A,B,C grasshopper selected objects are the A,B,C 3D letters created with Rhino. Python randomly selects one of those, everything good so far.

2.Now the A,B,C geometries are a mix of single and multiple geometries. The issue is that even though Python returns only one randomchoice, the matching 3D objects are mixed for some reason !

What am I missing here ?

What is good practice for manipulation of list of 3d objects ?