Loading node via the config loads it to /opt

I am loading a couple of nodes from GitHub via the configuration;

  - node-red-admin
  - git+https://github.com/borpin/node-red-contrib-fitbit2.git

The issue is that the nodes are then saved in /opt rather than locally in /opt/config/node-red/node_modules where (it seems) nodes installed via the palette are saved.

The knock on, is that if the node tries to write a file, it defaults to /opt rather than the user directory.

Is this location by design or a bug?