When Installing the cluster and unchecking the attach default network to install the cluster on secondary network it always pushes the value is true instead of false in the nodepool yaml.   

  platform:
    kubevirt:
      additionalNetworks:
      - name: default/localnet-nad-br-ex
      attachDefaultNetwork: true   <---- 

Even I am unchecking the box while installing the nodepool. 

   4.19.z 4.18.z  

    Create the cluster with additional network and post that remove the check box from the GUI nodepool and it still makes it as true post creation. 

    1. Create a HCP cluster using GUI and disable the defaultNetworkAttach 
    2. Check the yaml of the nodepool 
    3.
    

      platform:
    kubevirt:
      additionalNetworks:
      - name: default/localnet-nad-br-ex
      attachDefaultNetwork: true <---

platform:     kubevirt:       additionalNetworks:       - name: default/localnet-nad-br-ex       attachDefaultNetwork: false