Interaction between the particles in a clump

Hello,

I am interested at whether there is interaction between the particles in a clump. So I searched the questions and found one with the clarification that there is no interaction between the particles in a clump, see below:
https://answers.launchpad.net/yade/+question/403339

In this question, Mr. Jérôme Duriez answered with a example code:
******** Example **********
O.bodies.append(sphere(Vector3(0,0,0),1,fixed='True'))
O.bodies.append(sphere(Vector3(0,0,1.99),1,fixed='True'))
O.bodies.clump([0,1])
O.step()
O.interactions.has(0,1) # returns false here (true without O.bodies.clump() line)
***************************

He said that the example code will give a "False" at the end. However, I tried his example code and found that the result is "True". I tried many other times and found that there is interaction between the particles in a clump.

I am thinking that, if the bodies are generated by "O.bodies.append()" and are in contact with each other, even we clump them in the next step, the interactions between these bodies will not be removed, instead, these interactions will be in a constant state. Am I thinking correctly? I will be much appreciated if anyone could help me, thank you!

Regards,
Yuxuan Wen